busybox-syslog: add configuration file /etc/syslog.conf

busybox-syslog: add configuration file /etc/syslog.conf

By default, busybox has CONFIG_FEATURE_SYSLOGD_CFG enabled, but it
doesn't ship a configuration file.

This patch adds a configuration file (/etc/syslog.conf) to the
busybox-syslog package. This configuration file mainly serves as a
placeholder now.

The advantages of this change are:
1. Make the users aware of the fact that the /etc/syslog.conf file
   will actually be parsed by busybox's syslogd utility. And configuring
   that file will change the logging behaviour.
2. In a systemd based system, this file will prevent the same configuration
   file provided by the sysklogd package from messing things up.

[YOCTO #5066]

(From OE-Core rev: b7f6688f0700a1575037362af7a8ca94dccce471)

Signed-off-by: Chen Qi <Qi.Chen@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>