V4L/DVB: v4l: soc_camera: fix bound checking of mbus_fmt[] index

When code <= V4L2_MBUS_FMT_FIXED soc_mbus_get_fmtdesc returns a pointer to
mbus_fmt[x], where x < 0. Fix this.
Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
CC: stable@kernel.org
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

drivers/media/video/soc_mediabus.c

@@ -149,7 +149,8 @@ EXPORT_SYMBOL(soc_mbus_bytes_per_line);
 const struct soc_mbus_pixelfmt *soc_mbus_get_fmtdesc(
 	enum v4l2_mbus_pixelcode code)
 {
-	if ((unsigned int)(code - V4L2_MBUS_FMT_FIXED) > ARRAY_SIZE(mbus_fmt))
+	if (code - V4L2_MBUS_FMT_FIXED > ARRAY_SIZE(mbus_fmt) ||
+	    code <= V4L2_MBUS_FMT_FIXED)
 		return NULL;
 	return mbus_fmt + code - V4L2_MBUS_FMT_FIXED - 1;
 }