busybox: change syslog default to log to a file

busybox: change syslog default to log to a file

This changes the default in syslog-startup.conf to log messages
to a file (/var/log/messages) because:

a) we already mount /var/log as a volatile mount by default
b) users are accustomed to looking at /var/log/messages as
most distributions don't ship with logread

Signed-off-by: Joshua Lock <josh@linux.intel.com>