drm/radeon: consolidate rv770 uvd initialization and startup code.

drm/radeon: consolidate rv770 uvd initialization and startup code.

This match the exact same control flow as existing code. It just
use goto instead of multiple levels of if/else. It also clarify
early initialization failures by clearing rdev->has_uvd doing so
does not change end result from hardware point of view, it only
avoids printing more error messages down the line and thus only
the original error is reported.

Acked-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Jérôme Glisse <jglisse@redhat.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>