[AArch64][SVE] Asm: Support for saturing ADD/SUB instructions.

The variants added are:
    signed Saturating ADD/SUB (immediate)  e.g. sqadd z0.h, z0.h, #42
  unsigned Saturating ADD/SUB (immediate)  e.g. uqadd z0.h, z0.h, #42
    signed Saturating ADD/SUB (vectors)    e.g. sqadd z0.h, z0.h, z1.h
  unsigned Saturating ADD/SUB (vectors)    e.g. uqadd z0.h, z0.h, z1.h


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@336186 91177308-0d34-0410-b5e6-96231b3b80d8
9 files changed