drm/i915/bios: amend child device flags based on intel_vbt_decode

Copy over some fields defined in the intel_vbt_decode tool. No
functional changes.

Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/bce6907fa24d80643b33d58091d7675ff3b4f30e.1503670197.git.jani.nikula@intel.com