[AMDGPU] gfx11 scalar alu instructions

MC layer support for SOP(scalar alu operations) including encoding
support for s_delay_alu and s_sendmsg_rtn.

Contributors:
Jay Foad <jay.foad@amd.com>

Patch 7/N for upstreaming of AMDGPU gfx11 architecture.

Depends on D125319

Reviewed By: #amdgpu, arsenm

Differential Revision: https://reviews.llvm.org/D125498