drm/amdgpu: unify rlc function into structure

Put function rlc_init,rlc_fini,rlc_resume,rlc_stop,rlc_start into structure
amdgpu_rlc_funcs and change the method to call rlc function for each verssion of
GFX.

Signed-off-by: Likun Gao <Likun.Gao@amd.com>
Acked-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>