drm/i915: Populate fb->format early for inherited fbs

Make sure the framebuffer format info is available as early as possible
for fbs we inherit from the BIOS. This will allow us to use the fb as
if it was fully formed before we register it.

Cc: intel-gfx@lists.freedesktop.org
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1479498793-31021-22-git-send-email-ville.syrjala@linux.intel.com


Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>