[media] touptek: cast char types on %x printk

This fixes those two smatch warnings:
	drivers/media/usb/gspca/touptek.c:206 val_reply() warn: argument 3 to %02x specifier has type 'char'
	drivers/media/usb/gspca/touptek.c:222 reg_w() warn: argument 4 to %02x specifier has type 'char'

Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>