media: Kconfig: fix DVB dependencies

If I2C is present and it is module, the DVB core should also
be a module, otherwise build will now fail with:

  drivers/media/dvb-core/dvbdev.o: In function `dvb_module_probe':
     drivers/media/dvb-core/dvbdev.c:965: undefined reference to `i2c_new_device'
     drivers/media/dvb-core/dvbdev.c:972: undefined reference to `i2c_unregister_device'

Reported-by: kbuild test robot <fengguang.wu@intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>