V4L/DVB (3820): Drivers/media/dvb/dvb-usb/: possible cleanups

- make the following needlessly global struct static:
  dvb-usb/cxusb.c: cxusb_mt352_config

Signed-off-by: Adrian Bunk <bunk@stusta.de>
Signed-off-by: Michael Krufky <mkrufky@linuxtv.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>