amd/amdgpu: Limit rlcg write registers only for nv12

Create gfx_v10_0_rlc_funcs_sriov for nv12 with rlcg_write function pointers be initialized
so driver can use RLCG to write aceess CSIB and CP_ME_CNTL registers when nv12 in sriov mode

Signed-off-by: shaoyunl <shaoyun.liu@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>