radv: fix use-after-free upon GS copy shader cache hits
If radv_pipeline_cache_insert_shaders() finds a GS copy shader in the cache, it will free the variant in gs_variants and replace it with the one in the cache. Signed-off-by:Rhys Perry <pendingchaos02@gmail.com> Reviewed-by:
Samuel Pitoiset <samuel.pitoiset@gmail.com> Cc: mesa-stable Part-of: <!10433>