initramfs-framework: drop redundant /var/lock directory creation

initramfs-framework: drop redundant /var/lock directory creation

base-files already provides /var/lock as a symbolic link to /run/lock, and
since /run is created and mounted as tmpfs during init, there is no need
to explicitly create /var/lock within initramfs.

This avoids the following spurious error during boot:

    mkdir: can't create directory '/var/lock': No such file or directory

Signed-off-by: Ricardo Salveti <ricardo@foundries.io>
Signed-off-by: Mathieu Dubois-Briand <mathieu.dubois-briand@bootlin.com>
Signed-off-by: Ross Burton <ross.burton@arm.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>