drm/radeon: fix UVD suspend error

I met a bug recently and the kernel log:

[  330.171875] radeon 0000:03:00.0: couldn't schedule ib
[  330.175781] [drm:radeon_uvd_suspend [radeon]] *ERROR* Error destroying UVD (-22)!

In radeon drivers, using UVD suspend is as follows:

if (rdev->has_uvd) {
        uvd_v1_0_fini(rdev);
        radeon_uvd_suspend(rdev);
}

In radeon_ib_schedule function, we check the 'ring->ready' state,
but in uvd_v1_0_fini funciton, we've cleared the ready state.
So, just modify the suspend code flow to fix error.

Reviewed-by: Leo Liu <leo.liu@amd.com>
Signed-off-by: Qiang Ma <maqianga@uniontech.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>