[ARM] Do not convert some vmov instructions

Summary:
Patch https://reviews.llvm.org/D44467 implements conversion of invalid
vmov instructions into valid ones. It turned out that some valid
instructions also get converted, for example

  vmov.i64 d2, #0xff00ff00ff00ff00 ->
  vmov.i16 d2, #0xff00

Such behavior is incorrect because according to the ARM ARM section
F2.7.7 Modified immediate constants in T32 and A32 Advanced SIMD
instructions, "On assembly, the data type must be matched in the table
if possible."

This patch fixes the isNEONmovReplicate check so that the above
instruction is not modified any more.

Reviewers: rengolin, olista01

Reviewed By: rengolin

Subscribers: javed.absar, kristof.beyls, rogfer01, llvm-commits

Differential Revision: https://reviews.llvm.org/D44678

llvm-svn: 329158