[AVX-512] Simplify handling of INTR_TYPE_1OP_MASK_RM to remove support for the...

[AVX-512] Simplify handling of INTR_TYPE_1OP_MASK_RM to remove support for the second opcode since its never used. This makes it consistent with INTR_TYPE_2OP_MASK_RM and INTR_TYPE_3OP_MASK_RM.

And even if it was used we were passing the same operands to both so it wouldn't make sense to have two opcodes.

llvm-svn: 282051