s390/vmur: fix virtual vs physical address confusion

Add missing virt_to_phys() / phys_to_virt() translation to
alloc_chan_prog() and free_chan_prog().
This doesn't fix a bug since virtual and physical addresses
are currently the same.

Signed-off-by: Thomas Richter <tmricht@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>