yocto/kas: Explicit include for the pinned repository file

The KAS lockfile feature is able to include implicitly a file
having a name <filename>.lock.<ext> when processing another
KAS file <filename>.<ext>, this is convenient for overriding
settings and in this case is used to pin the repository to
a certain SHA.

However it has been tested that using --update argument will
bump the repository SHA as the lockfile was never included.

For this reason explicitly include the pinned repository file
and change its name in order not to trigger the KAS lockfile
feature.

Signed-off-by: Luca Fancellu <luca.fancellu@arm.com>