integritysetup: Add PHMAC algorithm to list of known algorithms

integritysetup: Add PHMAC algorithm to list of known algorithms

Add the PHMAC integrity algorithm to the list of supported algorithms.

The PHMAC algorithm is like the regular HMAC algorithm, but it takes a wrapped key
as input. A key for the PHMAC algorithm is an opaque key blob, who's physical size
has nothing to do with the cryptographic size. Currently PHMAC is only available
for the s390x architecture.