drm/i915/display: Wait for vblank in case of PSR is using trans push

drm/i915/display: Wait for vblank in case of PSR is using trans push

In case PSR uses trans push as a "frame change" event and we need to wait
vblank after triggering PSR "frame change" event. Otherwise we may miss
selective updates.

DSB skips all waits while PSR is active. Check push send is skipped as well
because trans push send bit is not reset by the HW if VRR is not enabled ->
we may start configuring new selective update while previous is not
complete. Avoid this by waiting for vblank after sending trans push.

v2: some typos fixed

Signed-off-by: Jouni Högander <jouni.hogander@intel.com>
Reviewed-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
Link: https://patch.msgid.link/20260127124120.1069026-8-jouni.hogander@intel.com