[AArch64][SVE] Asm: Support for ADR instruction.

Supporting various addressing modes:
- adr z0.s, [z0.s, z0.s]
- adr z0.s, [z0.s, z0.s, lsl #<shift>]
- adr z0.d, [z0.d, z0.d]
- adr z0.d, [z0.d, z0.d, lsl #<shift>]
- adr z0.d, [z0.d, z0.d, uxtw #<shift>]
- adr z0.d, [z0.d, z0.d, sxtw #<shift>]

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

Reviewed By: SjoerdMeijer

Differential Revision: https://reviews.llvm.org/D48870

llvm-svn: 336533