common: fix possible build problem without password support
In the case where CONFIG_PASSWORD is off, CONFIG_PASSWORD_DEFAULT is
undefined. As undefined is not "", this causes make to call find -type f.
If there is a filename containing a :, make will complain about having
"multiple target patterns"
Signed-off-by: Jan Luebbe <jlu@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>