drm/amdgpu: fix gmc init fail in sriov mode

"adev->gfx.rlc.rlcg_reg_access_supported = true;"
the above varible were set too late during driver initialization.
it will cause the driver to fail to write/read register during GMC hw init
in sriov mode.

move gfx_xxx_init_rlcg_reg_access_ctrl() function to gfx early init stage
to avoid this issue.

Fixes: 5d447e29 ("drm/amdgpu: add helper for rlcg indirect reg access")

Signed-off-by: Yang Wang <KevinYang.Wang@amd.com>
Reviewed-by: Hawking Zhang <Hawking.Zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>