AMDGPU/GFX12: Add new dot4 fp8/bf8 instructions (#77892)

Endoding is VOP3P. Tagged as deep/machine learning instructions. i32
type (v4fp8 or v4bf8 packed in i32) is used for src0 and src1. src0 and
src1 have no src_modifiers. src2 is f32 and has src_modifiers: f32
fneg(neg_lo[2]) and f32 fabs(neg_hi[2]).

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Co-authored-by: Petar Avramovic <Petar.Avramovic@amd.com>