radv: Fix pipeline cache locking issues
Need to lock around the whole process of retrieving cached shaders, and around GetPipelineCacheData. This fixes GPU hangs observed when creating multiple pipelines in parallel, which appeared to be due to invalid shader code being pulled from the cache. Signed-off-by:Alex Smith <asmith@feralinteractive.com> Reviewed-by:
Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>