drm/i915/fbc: Split plane size vs. surface size checks apart

Do separate checks for the visible plane size vs. the surface
size (which I take to mean offset+size). For now both use the
same max w/h, but we can relax the surface size limits as
a followup.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20231117171833.25816-1-ville.syrjala@linux.intel.com


Reviewed-by: Juha-Pekka Heikkila <juhapekka.heikkila@gmail.com>