[media] au0828: use pr_foo macros

Instead of using printk(KERN_foo, use pr_foo() macros.

No functional changes.

Note: we should do the same for dprintk(), but that would
require to remove the dprintk levels. So, for now, let's
not touch on it.

Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>