sysvinit: adjust boot sequence and remove hack from udev

sysvinit: adjust boot sequence and remove hack from udev

Adjust the boot sequence in sysvinit based systems.

The mountall.sh (mounting the local file system) needs to be started
before udev and bootlogd.

This patch makes mountall.sh start before udev and removes the hack of
mounting tmpfs in the udev init script.

This patch also adds some comments to the udev init script to make it
clear why we create the '/var/volatile/tmp' directory.

[YOCTO #5273]

Signed-off-by: Chen Qi <Qi.Chen@windriver.com>
Signed-off-by: Saul Wold <sgw@linux.intel.com>