[media] dvb-usb-v2: fix Kconfig dependency when RC_CORE=m

[media] dvb-usb-v2: fix Kconfig dependency when RC_CORE=m

It is not allowed to build driver as a build-in when RC_CORE
(remote controller support) is build as a module.
randconfig build error with next-20130719, in drivers/media/usb
drivers/built-in.o: In function `dvb_usbv2_disconnect':
(.text+0x154b39): undefined reference to `rc_unregister_device'
drivers/built-in.o: In function `dvb_usbv2_init_work':
dvb_usb_core.c:(.text+0x155b2d): undefined reference to `rc_allocate_device'
dvb_usb_core.c:(.text+0x155c38): undefined reference to `rc_register_device'
dvb_usb_core.c:(.text+0x155c5b): undefined reference to `rc_free_device'
drivers/built-in.o: In function `anysee_rc_query':
anysee.c:(.text+0x157795): undefined reference to `rc_keydown'

Reported-by: Jim Davis <jim.epost@gmail.com>
Signed-off-by: Antti Palosaari <crope@iki.fi>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>