sysvinit: bootlogd: ensure /var/log/boot is created in volatiles

sysvinit: bootlogd: ensure /var/log/boot is created in volatiles

bootlogd does not write to /var/log/boot if it does not exist,
so if using the volatiles facility (presumed to mount /var/log under a
tmpfs), ensure that /var/log/boot gets created.

Signed-off-by: Richard Tollerton <rich.tollerton@ni.com>
Signed-off-by: Ben Shelton <ben.shelton@ni.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>