[media] mceusb: use %*ph for small buffer dumps

It makes the printk cleaner. As a side efect, it also fixes those smatch
warnings:
	drivers/media/rc/mceusb.c:590 mceusb_dev_printdata() warn: argument 6 to %02x specifier has type 'char'
	drivers/media/rc/mceusb.c:590 mceusb_dev_printdata() warn: argument 7 to %02x specifier has type 'char'

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