media: cxusb-analog: fix V4L2 dependency

media: cxusb-analog: fix V4L2 dependency

CONFIG_DVB_USB_CXUSB_ANALOG is a 'bool' symbol with a dependency on the
tristate CONFIG_VIDEO_V4L2, which means it can be enabled as =y even
when its dependency is =m. This leads to a link failure:

drivers/media/usb/dvb-usb/cxusb-analog.o: In function `cxusb_medion_analog_init':
cxusb-analog.c:(.text+0x92): undefined reference to `v4l2_subdev_call_wrappers'
drivers/media/usb/dvb-usb/cxusb-analog.o: In function `cxusb_medion_register_analog':
cxusb-analog.c:(.text+0x466): undefined reference to `v4l2_device_register'
cxusb-analog.c:(.text+0x4c3): undefined reference to `v4l2_i2c_new_subdev'
cxusb-analog.c:(.text+0x4fb): undefined reference to `v4l2_subdev_call_wrappers'
...

Change the dependency only disallow the analog portion of the driver
in that configuration.

Fixes: e478d4054054 ("media: cxusb: add analog mode support for Medion MD95700")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Sean Young <sean@mess.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>