drm/i915/bios: remove the raw version of child device config

drm/i915/bios: remove the raw version of child device config

Convert the only user of the raw field, switching to the recently added
struct fields. No functional changes.

Cc: Animesh Manna <animesh.manna@intel.com>
Cc: Paulo Zanoni <paulo.r.zanoni@intel.com>
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/83e6a2058553a43e0d08a49df1f86821f38b206b.1503600621.git.jani.nikula@intel.com