As reported by Jim Davis <jim.epost@gmail.com>,
building with:
	CONFIG_USB=m
	CONFIG_SMS_USB_DRV=m
	CONFIG_SMS_SDIO_DRV=y
	CONFIG_SMS_SIANO_MDTV=y
	CONFIG_SMS_SIANO_DEBUGFS=y

causes a build error:

	drivers/built-in.o: In function `smsdvb_debugfs_register':
	/home/jim/linux/drivers/media/common/siano/smsdvb-debugfs.c:537:
	undefined reference to `usb_debug_root'
	make: *** [vmlinux] Error 1

That happens because the siano-mdtv is builtin, while USB is a
module. As it makes not much sense to have sms-usb compiled as 'm'
and sms-sdio compiled as 'y' (or vice-versa), only allow enabling
debugfs if both are either 'y' or 'm'.
Reported-by: Jim Davis <jim.epost@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>