V4L/DVB (9678): af9015: Cleanup switch for usb ID

It is much more readable to swap the byteorder in the switch rather
than in each case statement.

Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>