lavd/v4l2: do not fail when VIDIOC_ENUMSTD returns ENODATA

As of September 14 2012, v4l_enumstd() will return ENODATA
when a device's std field is set to 0. That is, the device
does not have a standard format. In order to properly
handle this case, v4l2_set_parameters should catch the
ENODATA code and break instead of failing.

Below is the v4l2-core commit describing this change.

>>commit a5338190efc7cfa8c99a6856342a77d21c9a05cf
>>Author: Hans Verkuil <hans.verkuil@cisco.com>
>>Date:   Fri Sep 14 06:45:43 2012 -0300
>>
>>    [media] v4l2-core: tvnorms may be 0 for a given input, handle that case
>>
>>    Currently the core code looks at tvnorms to see whether ENUMSTD
>>    or G_PARM should be enabled. This is not a good check for drivers
>>    that support the STD API on one input and the DV Timings API on another.
>>    In that case tvnorms may be 0.
>>    Instead check whether s_std is present (for ENUMSTD) or whether g_std or
>>    current_norm is present for g_parm.
>>    Also, in the enumstd core function return ENODATA if tvnorms is 0,
>>    because in that case the current input does not support the STD API
>>    and ENUMSTD should return ENODATA for that.
>>
>>    Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
>>    Reviewed-by: Sakari Ailus <sakari.ailus@iki.fi>
>>    Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

libavdevice/v4l2.c

@@ -688,7 +688,7 @@ static int v4l2_set_parameters(AVFormatContext *s1)
             standard.index = i;
             if (v4l2_ioctl(s->fd, VIDIOC_ENUMSTD, &standard) < 0) {
                 ret = AVERROR(errno);
-                if (ret == AVERROR(EINVAL)) {
+                if (ret == AVERROR(EINVAL) || ret == AVERROR(ENODATA)) {
                     tpf = &streamparm.parm.capture.timeperframe;
                     break;
                 }