config: PID_FILE_PATH required for FEATURE_CROND_SPECIAL_TIMES

config: PID_FILE_PATH required for FEATURE_CROND_SPECIAL_TIMES

When crond is built with FEATURE_CROND_SPECIAL_TIMES enabled, it creates
a file called 'crond.reboot' at CONFIG_PID_FILE_PATH, but if
FEATURE_PIDFILE is disabled, this will be an empty string and the file
will be created in the root directory, which is undesirable.

This commit makes PID_FILE_PATH depend on FEATURE_CROND_SPECIAL_TIMES as
well as FEATURE_PIDFILE so that you get sensible behaviour in crond when
FEATURE_PIDFILE is switched off.

Signed-off-by: James Byrne <james.byrne@origamienergy.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>