Use bitset for assembler predicates

AMDGPU target run out of Subtarget feature flags hitting the limit of 64.
AssemblerPredicates uses at most uint64_t for their representation.
At the same time CodeGen has exhausted this a long time ago and switched
to a FeatureBitset with the current limit of 192 bits.

This patch completes transition to the bitset for feature bits extending
it to asm matcher and MC code emitter.

Differential Revision: https://reviews.llvm.org/D59002

llvm-svn: 355839