main/busybox: fix klogd dependency on logger

klogd depends on a syslog implementation for its output, but it
does not have to be 'syslog': syslog, rsyslog and syslog-ng all
provide a 'logger' virtual target which klogd can depend on.

(regardless of the fact that more sophisticated syslog implementations
can read from kernel logs directly and probably do not need klogd...)