APM: take over maintainership

Commit 04a6553f ("apm: orphan the driver") Orphaned the APM
driver as Stephen is not willing/able to maintain it any more.

As I still have some hardware that is using APM and running 2.6,
I can take it over.

Signed-off-by: Jiri Kosina <jkosina@suse.cz>