drm: Don't generate invalid AVI infoframes for CEA modes

From CEA-861:

  Data Byte 1, bit A0 indicates whether Active Format Data is present in
  Data Byte 2 bits R3 through R0. A source device shall set A0=1 when
  any of the AFD bits are set.

ie. if we want to set active_aspect, we need to set the
active_info_valid bit to 1 as well.

Cc: Thierry Reding <thierry.reding@avionic-design.de>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Damien Lespiau <damien.lespiau@intel.com>
Acked-by: Dave Airlie <airlied@gmail.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>