[media] tw5864: use dev_warn instead of WARN to shut up warning

tw5864_frameinterval_get() only initializes its output when it successfully
identifies the video standard in tw5864_input. We get a warning here because
gcc can't always track the state if initialized warnings across a WARN()
macro, and thinks it might get used incorrectly in tw5864_s_parm:

media/pci/tw5864/tw5864-video.c: In function 'tw5864_s_parm':
media/pci/tw5864/tw5864-video.c:816:38: error: 'time_base.numerator' may be used uninitialized in this function [-Werror=maybe-uninitialized]
media/pci/tw5864/tw5864-video.c:819:31: error: 'time_base.denominator' may be used uninitialized in this function [-Werror=maybe-uninitialized]

Using dev_warn() instead of WARN() avoids the __branch_check__() in
unlikely and lets the compiler see that the initialization is correct.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Andrey Utkin <andrey.utkin@corp.bluecherry.net>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

drivers/media/pci/tw5864/tw5864-video.c

@@ -716,6 +716,8 @@ static void tw5864_frame_interval_set(struct tw5864_input *input)
 static int tw5864_frameinterval_get(struct tw5864_input *input,
 				    struct v4l2_fract *frameinterval)
 {
+	struct tw5864_dev *dev = input->root;
+
 	switch (input->std) {
 	case STD_NTSC:
 		frameinterval->numerator = 1001;
@@ -727,8 +729,8 @@ static int tw5864_frameinterval_get(struct tw5864_input *input,
 		frameinterval->denominator = 25;
 		break;
 	default:
-		WARN(1, "tw5864_frameinterval_get requested for unknown std %d\n",
-		     input->std);
+	        dev_warn(&dev->pci->dev, "tw5864_frameinterval_get requested for unknown std %d\n",
+			 input->std);
 		return -EINVAL;
 	}