[Why]
If VSTARTUP changes due to bandwidth requirements, we must
recalculate and update VLINE2 as well for proper flip reporting.

[How]
After all calls to program_global_sync which reconfigures
VSTARTUP, also make sure to update V_UPDATE (i.e. VLINE2 on DCNx).
Signed-off-by: NAric Cyr <aric.cyr@amd.com>
Reviewed-by: NSivapiriyan Kumarasamy <Sivapiriyan.Kumarasamy@amd.com>
Acked-by: NBhawanpreet Lakha <Bhawanpreet.Lakha@amd.com>
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>