drm/amd/display: Fix notification of vtotal to DMU for cursor offload

drm/amd/display: Fix notification of vtotal to DMU for cursor offload

[Why]
It was placed after the early return and the notification is never sent.

[How]
Place it after .set_drr and before the return.

Reviewed-by: Alvin Lee <alvin.lee2@amd.com>
Signed-off-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Signed-off-by: Wayne Lin <wayne.lin@amd.com>
Tested-by: Dan Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>