V4L/DVB: Video : pwc : Fix regression in pwc_set_shutter_speed caused by bad constant => sizeof conversion.

Regression was caused by my commit 6b35ca0d3d586b8ecb8396821af21186e20afaf0
which determined message size using sizeof rather than hardcoded constants.

Unfortunately pwc_set_shutter_speed reuses a 2 byte buffer for a one byte
message too so the sizeof was bogus in this case.

All other uses of sizeof checked and are ok.

Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: stable@kernel.org
Signed-off-by: Martin Fuzzey <mfuzzey@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

drivers/media/video/pwc/pwc-ctrl.c

@@ -753,7 +753,7 @@ int pwc_set_shutter_speed(struct pwc_device *pdev, int mode, int value)
 		buf[0] = 0xff; /* fixed */
 
 	ret = send_control_msg(pdev,
-		SET_LUM_CTL, SHUTTER_MODE_FORMATTER, &buf, sizeof(buf));
+		SET_LUM_CTL, SHUTTER_MODE_FORMATTER, &buf, 1);
 
 	if (!mode && ret >= 0) {
 		if (value < 0)