V4L/DVB (4105): Remove uneeded prototype

Uneeded extern prototype is removed, as the function is 
prototyped at media/v4l2-common.h.
Signed-off-by: Trent Piepho <xyzzy@speakeasy.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>

drivers/media/video/pwc/pwc-v4l.c

@@ -210,10 +210,6 @@ static struct v4l2_queryctrl pwc_controls[] = {
 	},
 };
 
-#if CONFIG_PWC_DEBUG
-/* In 2.6.16-rc1 v4l_printk_ioctl is not defined but exported */
-extern void v4l_printk_ioctl(unsigned int cmd);
-#endif
 
 static void pwc_vidioc_fill_fmt(const struct pwc_device *pdev, struct v4l2_format *f)
 {