drm/i915/bios: Introduce panel_bits() and panel_bool()

Abstract the bit extraction from the VBT per-panel bitfields
slightly.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220615151445.8531-3-ville.syrjala@linux.intel.com


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