s390/qeth: add phys_to_virt() translation for AOB

Data addresses in the AOB are absolute, and need to be translated before
being fed into kmem_cache_free(). Currently this phys_to_virt() is a no-op.
Also see commit 2db01da8

 ("s390/qdio: fill SBALEs with absolute addresses").

Signed-off-by: Julian Wiedmann <jwi@linux.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>