drm/i915: Introduce scaled_planes bitmask

Add another plane bitmask, this time tracking which planes are
scaled. This is going to be useful in ILK watermark computations,
and skl+ pipe scaler assignments.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220211090629.15555-4-ville.syrjala@linux.intel.com


Reviewed-by: Jani Nikula <jani.nikula@intel.com>