Update version and change download URL to kernel.org.

The new version contans a pkgconfig file, which is required by, for
example, bcachefs-tools.

When we use EPREFIX=, libkeyutils.pc is created in /lib/pkgconfig
instead of /usr/lib/pkgconfig where it is searched for.

So return to the default EPREFIX (/usr).

A link or symlink /sbin/request-key --> /usr/sbin/requestk-key needs to
be installed when this package is updated. We don't do this from this
package, because that would be obsolete when we do the usr-merge and the
package would needed to be updated again.