drm/edid: Add packed attribute to new gtf2 and cvt structs

The new structs added in struct detailed_data_monitor_range must be
marked with packed attribute although the outer struct itself is
already marked as packed.  Otherwise these 7-bytes structs may be
aligned, and give the wrong position and size for the data.

Signed-off-by: Takashi Iwai <tiwai@suse.de>
Acked-by: Adam Jackson <ajax@redhat.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>