s390/vfio-ap: fix kernel doc and signature of group notifier functions

The vfio_ap device driver registers a group notifier function to handle
the VFIO_GROUP_NOTIFY_SET_KVM event signalling the KVM pointer has been
set or cleared. There are two helper functions invoked by the handler
function: One called when the KVM pointer has been set, and the other
when the pointer is cleared.

The kernel doc for both of these functions contains a comment introduced
by commit 0cc00c8d (s390/vfio-ap: fix circular lockdep when
setting/clearing crypto masks) that is no longer valid. This patch removes
this comment from the kernel doc of each helper function.

Commit 86956e70 (s390/vfio-ap: replace open coded locks for
VFIO_GROUP_NOTIFY_SET_KVM notification) added a parameter to the signature
of the helper function that handles the event indicating the KVM pointer
has been cleared. The parameter added was the KVM pointer itself.
One of the function's primary purposes is to clear the KVM pointer from the
ap_matrix_mdev instance in which it is stored. Since the callers of this
function derive the KVM pointer passed to the function from the
ap_matrix_mdev object itself, it is completely unnecessary to include this
parameter in the function's signature since it can simply be retrieved from
the ap_matrix_mdev object which is also passed in. This patch removes the
KVM pointer from the function's signature.

Signed-off-by: Tony Krowiak <akrowiak@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>