media: em28xx: make v4l2-compliance happier by starting sequence on zero

BugLink: https://bugs.launchpad.net/bugs/1810947

commit afeaade9 upstream.

The v4l2-compliance tool complains if a video doesn't start
with a zero sequence number.

While this shouldn't cause any real problem for apps, let's
make it happier, in order to better check the v4l2-compliance
differences before and after patchsets.

This is actually an old issue. It is there since at least its
videobuf2 conversion, e. g. changeset 3829fadc461 ("[media]
em28xx: convert to videobuf2"), if VB1 wouldn't suffer from
the same issue.

Cc: stable@vger.kernel.org
Fixes: d3829fad ("[media] em28xx: convert to videobuf2")
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Juerg Haefliger <juergh@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

drivers/media/usb/em28xx/em28xx-video.c

@@ -1149,6 +1149,8 @@ static void em28xx_ctrl_notify(struct v4l2_ctrl *ctrl, void *priv)
 {
 	struct em28xx *dev = priv;
 
+	dev->v4l2->field_count = 0;
+
 	/*
 	 * In the case of non-AC97 volume controls, we still need
 	 * to do some setups at em28xx, in order to mute/unmute