kernel: set WATCHDOG_CORE dependency in kmod-hwmon-sch5627

kernel: set WATCHDOG_CORE dependency in kmod-hwmon-sch5627

For many target we have added CONFIG_WATCHDOG_CORE=y to the target
config due to the following error:

 Package kmod-hwmon-sch5627 is missing dependencies for the following
 libraries:
 watchdog.ko

However, actually the proper way appears to be setting the
dependency for the kmod-hwmon-sch5627 package, as the error message
demands.

Do this in this patch and remove the target config entries added
due to this issue.

Signed-off-by: Adrian Schmutzler <freifunk@adrianschmutzler.de>