Revert r355224 "[TableGen][SelectionDAG][X86] Add specific isel matchers for...

Revert r355224 "[TableGen][SelectionDAG][X86] Add specific isel matchers for immAllZerosV/immAllOnesV. Remove bitcasts from X86 patterns that are no longer necessary."

This caused the first matcher in the isel table for many targets to Opc_Scope instead of Opc_SwitchOpcode. This leads to a significant increase in isel match failures.

llvm-svn: 355433