If the USB driver is enabled but the demodulator is not, we get a link error:
ERROR: "zd1301_demod_get_dvb_frontend" [drivers/media/usb/dvb-usb-v2/zd1301.ko] undefined!
ERROR: "zd1301_demod_get_i2c_adapter" [drivers/media/usb/dvb-usb-v2/zd1301.ko] undefined!
Such a configuration obviously makes no sense, but we should not fail
the build. This tries to mimic what we have for other drivers by turning
the build failure into a runtime failure.
Alternatively we could use an unconditional 'select' or 'depends on' to enforce
a sane configuration.
Fixes: 47d65372b3 ("[media] zd1301_demod: ZyDAS ZD1301 DVB-T demodulator driver")
Fixes: 992b39872b ("[media] zd1301: ZyDAS ZD1301 DVB USB interface driver")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>