media: media.h.rst.exceptions: ignore MEDIA-ENT-F-DTV-DECODER

This was kept just for backward compatibility. Solves this warning:
	media.h.rst:6: WARNING: undefined label: media-ent-f-dtv-decoder (if the link has no caption the label must precede a section header)
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>

Documentation/media/media.h.rst.exceptions

@@ -6,10 +6,10 @@ ignore define MEDIA_API_VERSION
 ignore define MEDIA_ENT_F_BASE
 ignore define MEDIA_ENT_F_OLD_BASE
 ignore define MEDIA_ENT_F_OLD_SUBDEV_BASE
+ignore define MEDIA_ENT_F_DTV_DECODER
 ignore define MEDIA_INTF_T_DVB_BASE
 ignore define MEDIA_INTF_T_V4L_BASE
 ignore define MEDIA_INTF_T_ALSA_BASE
-
 #ignore legacy entity type macros
 ignore define MEDIA_ENT_TYPE_SHIFT
 ignore define MEDIA_ENT_TYPE_MASK