drm/i915: Use plane->can_async_flip() for alignment exceptions

drm/i915: Use plane->can_async_flip() for alignment exceptions

Async flips often require bigger alignment that sync flips.
Currently we have HAS_ASYNC_FLIPS() checks strewn about to
inidcate that async flips are generally supported and thus
we want more alignment. Switch that over to using
intel_plane_can_async_flip() so that we can handle these
in a slightly less messy way. Currently we don't have cases
where async flips would require different alignment for
different modifiers on the same plane.

We'll also move the HAS_ASYNC_FLIPS() check to the plane init
code so that we can still use that as a quick way to disable
the async flips workarounds for testing purposes.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20241009182207.22900-5-ville.syrjala@linux.intel.com
Reviewed-by: Jouni Högander <jouni.hogander@intel.com>