[AArch64][SVE] Asm: Support for non-temporal, contiguous LDNT1/STNT1 load/store instructions.

Reviewers: fhahn, rengolin, samparker, SjoerdMeijer, javed.absar

Reviewed By: samparker

Differential Revision: https://reviews.llvm.org/D46269

llvm-svn: 331343