s390/ap: fix kernel doc comments

Get rid of warnings like:

drivers/s390/crypto/ap_bus.c:216: warning:
 bad line:
drivers/s390/crypto/ap_bus.c:444:
 warning: Function parameter or member 'floating' not described in 'ap_interrupt_handler'

Reviewed-by: Harald Freudenberger <freude@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>