kernel-install: allow to create $BOOT/$MACHINE_ID

Commit [cf73f650890](https://github.com/systemd/systemd/commit/cf73f650890

)
provides script `00-entry-directory.install` which creates the entry
directory only if `$BOOT/$MACHINE_ID` folder exists.
This part was moved out of `kernel-install` script and may introduce
the problem during upgrade since before Apertis v2022dev2 we do kernel
install with `$MACHINE_ID` generated in a build time. Later we remove
`/etc/machine-id` file allowing to generate an unique machine ID during
first boot, so there will be no directory `$BOOT/$MACHINE_ID` with a new
ID preventing from new entry generation during kernel upgrade in runtime.
Hence remove the part checking the `$BOOT/$MACHINE_ID` existence and
allow to create the proper entry in any case, returning the previous
`kernel-install` behaviour.

Signed-off-by: Denis Pynkin <denis.pynkin@collabora.com>