drm/amdgpu: Add RLCG interface driver implementation for gfx v9.4.3 (v3)

Add RLCG interface support for gfx v9.4.3 and multiple XCCs.
Do not enable it yet.

v2: Fix amdgpu_rlcg_reg_access_ctrl init, add support for multiple XCCs
    in amdgpu_mm_wreg_mmio_rlc

v3: Use GET_INST() when indexing amdgpu_rlcg_reg_access_ctrl

Signed-off-by: Victor Lu <victorchengchi.lu@amd.com>
Reviewed-by: Zhigang Luo <zhigang.luo@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>