drm/i915: Reuse vlv_primary_min_alignment() for sprites as well

Rename vlv_primary_min_alignment() to vlv_plane_min_alignment()
and use it to replace vlv_sprite_min_alignment() since the
behaviour is now identical when the plane init doesn't set up
any async flips stuff.

Technically VLV/CHV sprites do support async flips, so this
also makes us a bit more future proof if/when we extend async
flip support to more than one plane.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20241009182207.22900-6-ville.syrjala@linux.intel.com


Reviewed-by: Jouni Högander <jouni.hogander@intel.com>