[media] af9013: Don't accept invalid bandwidth

If userspace sends an invalid bandwidth, it should either return
EINVAL or switch to auto mode.

This driver will go past an array and program the hardware on a
wrong way if this happens.

Cc: stable@vger.kernel.org
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>