powerpc/spufs: Get rid of broken fasync stuff

In all the years it's been in the tree it had never been used by
anything - it would instantly trigger BUG_ON() in fs/fcntl.c due to
bogus band argument (ie. POLLIN not POLL_IN) passed to kill_fasync().
Since nobody had ever used it in ten years, let's just rip it out and be
done with that.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>