freedreno: Drop invalid scissor optimization.

We do support TF now, so it's no longer valid.  Besides, if we want this
optimization, we should probably have mesa/st doing it right for everyone.

Reviewed-by: Rob Clark <robdclark@gmail.com>
10 jobs for !923 with freedreno-cleanups in 9 minutes and 22 seconds (queued for 1 second)
detached
Status Name Job ID Coverage
  Containers Build
passed debian #337535

00:00:22

 
  Build+Test
passed meson-clang #337537

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passed meson-clover #337541

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passed meson-main #337540

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passed meson-swr-glvnd #337536

00:05:49

passed meson-vulkan #337542

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passed scons-llvm #337544

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passed scons-nollvm #337543

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passed scons-swr #337538

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passed scons-win64 #337539

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