drm/amdgpu/virt: change the place of virt_init_setting

Change place of virt_init_setting function so that can cover the
cg and pg flags configuration.

Signed-off-by: Xiangliang Yu <Xiangliang.Yu@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>