gallivm: Fix LLVM optimization with the new pass manager

The previous list of passes contained several errors: "constprop" does not exist anymore and a trailing ',' is not allowed. This made LLVMRunPasses fail, but the error is silently ignored. Thus none of the listed passes ran at all.

https://reviews.llvm.org/D85159 suggests "InstSimplify really should be used anywhere ConstProp is being used" so replace constprop with instsimplify and remove the trailing comma.

By enabling pass logging with LLVMPassBuilderOptionsSetDebugLogging(opts, true), the difference is visible. Before:

Running pass: AlwaysInlinerPass on [module]
Running analysis: InnerAnalysisManagerProxy<llvm::FunctionAnalysisManager, llvm::Module> on [module]
Running analysis: ProfileSummaryAnalysis on [module]
Running pass: CoroConditionalWrapper on [module]
Running pass: AnnotationRemarksPass on fs_variant_partial (1162 instructions)
Running analysis: TargetLibraryAnalysis on fs_variant_partial
Running pass: AnnotationRemarksPass on fs_variant_whole (1110 instructions)
Running analysis: TargetLibraryAnalysis on fs_variant_whole

After:

Running pass: AlwaysInlinerPass on [module]
Running analysis: InnerAnalysisManagerProxy<llvm::FunctionAnalysisManager, llvm::Module> on [module]
Running analysis: ProfileSummaryAnalysis on [module]
Running pass: CoroConditionalWrapper on [module]
Running pass: AnnotationRemarksPass on fs_variant_partial (1162 instructions)
Running analysis: TargetLibraryAnalysis on fs_variant_partial
Running pass: AnnotationRemarksPass on fs_variant_whole (1110 instructions)
Running analysis: TargetLibraryAnalysis on fs_variant_whole
Running analysis: InnerAnalysisManagerProxy<llvm::FunctionAnalysisManager, llvm::Module> on [module]
Running pass: SROAPass on fs_variant_partial (1162 instructions)
Running analysis: DominatorTreeAnalysis on fs_variant_partial
Running analysis: AssumptionAnalysis on fs_variant_partial
Running analysis: TargetIRAnalysis on fs_variant_partial
Running pass: EarlyCSEPass on fs_variant_partial (1111 instructions)
Running analysis: TargetLibraryAnalysis on fs_variant_partial
Running pass: SimplifyCFGPass on fs_variant_partial (961 instructions)
Running pass: ReassociatePass on fs_variant_partial (961 instructions)
Running pass: PromotePass on fs_variant_partial (897 instructions)
Running pass: InstCombinePass on fs_variant_partial (897 instructions)
Running analysis: OptimizationRemarkEmitterAnalysis on fs_variant_partial
Running analysis: AAManager on fs_variant_partial
Running analysis: BasicAA on fs_variant_partial
Running analysis: ScopedNoAliasAA on fs_variant_partial
Running analysis: TypeBasedAA on fs_variant_partial
Running analysis: OuterAnalysisManagerProxy<llvm::ModuleAnalysisManager, llvm::Function> on fs_variant_partial
Running pass: SROAPass on fs_variant_whole (1110 instructions)
Running analysis: DominatorTreeAnalysis on fs_variant_whole
Running analysis: AssumptionAnalysis on fs_variant_whole
Running analysis: TargetIRAnalysis on fs_variant_whole
Running pass: EarlyCSEPass on fs_variant_whole (1059 instructions)
Running analysis: TargetLibraryAnalysis on fs_variant_whole
Running pass: SimplifyCFGPass on fs_variant_whole (912 instructions)
Running pass: ReassociatePass on fs_variant_whole (912 instructions)
Running pass: PromotePass on fs_variant_whole (844 instructions)
Running pass: InstCombinePass on fs_variant_whole (844 instructions)
Running analysis: OptimizationRemarkEmitterAnalysis on fs_variant_whole
Running analysis: AAManager on fs_variant_whole
Running analysis: BasicAA on fs_variant_whole
Running analysis: ScopedNoAliasAA on fs_variant_whole
Running analysis: TypeBasedAA on fs_variant_whole
Running analysis: OuterAnalysisManagerProxy<llvm::ModuleAnalysisManager, llvm::Function> on fs_variant_whole

Fixes: 2037c34f ("gallivm: move to new pass manager to handle coroutines change.")