[media] radio-keene: add delay in order to settle hardware

It was found by trial and error testing that at least 11 ms delay is
needed before first I/O, otherwise device will skip given command.

Signed-off-by: Antti Palosaari <crope@iki.fi>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>