[media] af9035: various small changes for af9035_ctrl_msg()

Fix USB buffer len to maximum possible.
Various log writing fixes, remove extra new lines and excessive
type casts. Rename and type change some variables.

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