drm/i915/psr: Wait for idle only after possible send push

drm/i915/psr: Wait for idle only after possible send push

We are planning to move using trans push mechanism to trigger the Frame
Change event. In that case we can't wait PSR to idle before send push
happens. Due to this move wait for idle to be done after possible send push
is done.

This should be ok for Frame Change event triggered by register write as
well. Wait for idle is needed only for corner case where PSR is
transitioning into DEEP_SLEEP when Frame Change event is triggered. It just
has to be before wait for vblank. Otherwise we may have vblank before PSR
enters DEEP_SLEEP and still using old frame buffers for first frame after
wake up.

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/20260127124120.1069026-9-jouni.hogander@intel.com