amdgpu_kiq_wreg/rreg is hardcoded to use MEC engine 0.

Add an xcc_id parameter to amdgpu_kiq_wreg/rreg, define W/RREG32_XCC
and amdgpu_device_xcc_wreg/rreg to use the new xcc_id parameter.

Using amdgpu_sriov_runtime to determine whether to access via kiq or
RLC is sufficient for now.

v5: add condition in amdgpu_device_xcc_w/rreg, remove trace func call

v4: avoid using amdgpu_sriov_w/rreg

v3: use W/RREG32_XCC to handle non-kiq case

v2: define amdgpu_device_xcc_wreg/rreg instead of changing parameters
    of amdgpu_device_wreg/rreg
Signed-off-by: Victor Lu <victorchengchi.lu@amd.com>
Reviewed-by: Lijo Lazar <lijo.lazar@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>