systemd: enable kernel-msgs in journald
This patch enables systemd-journald to read and show kernel messages, so that it can be used by applications looking for important events in the system as a replacement for syslog-ng.
Note: As by the journald configuration concept (and yocto recipe organization) this change will result in a change to a "drop-in" config file located in "/lib/systemd/journald.cond.d/", while "/etc/systemd/journald.conf" still reflects the (different) compile-time defaults of systemd itself. This is weirdly confusing, but actually the way the poky-layer itself is doing it.