crc32c: Add crc32c function optimized for ppc architecture

crc32c: Add crc32c function optimized for ppc architecture

Add a performance optimized crc32c function for
ppc64le that uses Altivec assembly instructions.
Add an architecture probe for ppc (PowerPC
'ppc64le' architecture).  When the architecture
probe detects that the ppc specific crc32c function
(ceph_crc32c_ppc) can be used, it will do so instead
of using the default crc32c function (ceph_crc32c_sctp).

Signed-off-by: Andrew Solomon <asolomon@us.ibm.com>