s390/cmf: fix virtual vs physical address confusion

The measurement block origin address is an absolute address; therefore
add a missing virt_to_phys() translation to the cmf_activate() inline
assembly.

This doesn't fix a bug, since virtual and physical addresses are
currently identical.

Acked-by: Alexander Gordeev <agordeev@linux.ibm.com>
Acked-by: Vineeth Vijayan <vneethv@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>