Be consistent in that active_planes bitmask fits in a u8.
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210514125751.17075-4-ville.syrjala@linux.intel.comReviewed-by: NStanislav Lisovskiy <stanislav.lisovskiy@intel.com>