Extract intel_fbc_max_plane_size() from intel_fbc_plane_size_valid().
We'll have another use for this soon in determining how much stolen
memory we'd like to keep reserved for FBC.
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240705145254.3355-5-ville.syrjala@linux.intel.comReviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>