[media] si470x: fix compile warning

Tobias Lorenz <tobias.lorenz@gmx.net> has looked at this and agreed that the
'buf' variable could be removed.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
diff --git a/drivers/media/radio/si470x/radio-si470x-usb.c b/drivers/media/radio/si470x/radio-si470x-usb.c
index 4cf5370..a6ad707 100644
--- a/drivers/media/radio/si470x/radio-si470x-usb.c
+++ b/drivers/media/radio/si470x/radio-si470x-usb.c
@@ -395,7 +395,6 @@
 static void si470x_int_in_callback(struct urb *urb)
 {
 	struct si470x_device *radio = urb->context;
-	unsigned char buf[RDS_REPORT_SIZE];
 	int retval;
 	unsigned char regnr;
 	unsigned char blocknum;
@@ -423,7 +422,6 @@
 
 	if (urb->actual_length > 0) {
 		/* Update RDS registers with URB data */
-		buf[0] = RDS_REPORT;
 		for (regnr = 0; regnr < RDS_REGISTER_NUM; regnr++)
 			radio->registers[STATUSRSSI + regnr] =
 			    get_unaligned_be16(&radio->int_in_buffer[