V4L/DVB: gspca_xirlink_cit: support bandwidth changing for devices with 1 alt setting

Some xirlink_cit models have only 1 alt setting, but the actual used
bandwidth can be programmed through a register use this to allow streaming
while other isoc streams (for example sound) are active at the same time.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>