R600: Remove AMDILPeeopholeOptimizer and replace optimizations with tablegen patterns

The BFE optimization was the only one we were actually using, and it was
emitting an intrinsic that we don't support.

https://bugs.freedesktop.org/show_bug.cgi?id=64201



Reviewed-by: Christian König <christian.koenig@amd.com>

NOTE: This is a candidate for the 3.3 branch.
llvm-svn: 181580