drm/edid: Do drm_dmt_modes_for_range() for all range descriptor types

EDID 1.4 retcons the meaning of the "GTF feature" bit to mean "is
continuous frequency", and moves the set of supported timing formulas
into the range descriptor itself.  In any event, the range descriptor
can act as a filter on the DMT list without regard to a specific timing
formula.

Signed-off-by: Adam Jackson <ajax@redhat.com>
Tested-by: Takashi Iwai <tiwai@suse.de>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>