drm/amdgpu: initialize RAS for gfx_v9_4_3

Register GFX RAS functions and initialize GFX RAS.

v2: remove xcp operations.
v3: reuse the return value of gfx_ras_sw_init.

Signed-off-by: Tao Zhou <tao.zhou1@amd.com>
Reviewed-by: Hawking Zhang <Hawking.Zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>