[AArch64][SVE] Asm: Support for contiguous LD1 (scalar+imm) load instructions

Reviewers: fhahn, rengolin, javed.absar, huntergr, SjoerdMeijer, t.p.northover, echristo, evandro

Reviewed By: rengolin

Subscribers: tschuett, llvm-commits, kristof.beyls

Differential Revision: https://reviews.llvm.org/D45618

llvm-svn: 330024