V4L/DVB: dvb-core: fix initialization of feeds list in demux filter

A DVB demultiplexer device can be used to set up either a PES filter or
a section filter. In the former case, the ts field of the feed union of
struct dmxdev_filter is used, in the latter case the sec field of the
same union is used.
The ts field is a struct list_head, and is currently initialized in the
open() method of the demux device. When for a given demuxer a section
filter is set up, the sec field is played with, thus if a PES filter
needs to be set up after that the ts field will be corrupted, causing a
kernel oops.
This fix moves the list head initialization to
dvb_dmxdev_pes_filter_set(), so that the ts field is properly
initialized every time a PES filter is set up.

Signed-off-by: Francesco Lavra <[e-mail]>
Cc: stable <[e-mail]>
Reviewed-by: Andy Walls <[e-mail]>
Tested-by: hermann pitton <[e-mail]>
Signed-off-by: Mauro Carvalho Chehab <[e-mail]>

drivers/media/dvb/dvb-core/dmxdev.c

···
 	dvb_ringbuffer_init(&dmxdevfilter->buffer, NULL, 8192);
 	dmxdevfilter->type = DMXDEV_TYPE_NONE;
 	dvb_dmxdev_filter_state_set(dmxdevfilter, DMXDEV_STATE_ALLOCATED);
-	INIT_LIST_HEAD(&dmxdevfilter->feed.ts);
 	init_timer(&dmxdevfilter->timer);
 
 	dvbdev->users++;
···
 	dmxdevfilter->type = DMXDEV_TYPE_PES;
 	memcpy(&dmxdevfilter->params, params,
 	       sizeof(struct dmx_pes_filter_params));
+	INIT_LIST_HEAD(&dmxdevfilter->feed.ts);
 
 	dvb_dmxdev_filter_state_set(dmxdevfilter, DMXDEV_STATE_SET);