ossl: Add support for powerpc64/powerpc64le

Summary:
Add support for building ossl(4) on powerpc64* by implementing ossl_cpuid and
other support functions for powerpc. The required assembly files for ppc were
already present in-tree.

Test Plan: The changes were tested using the in-tree tools/tools/crypto/cryptocheck.c tool on both powerpc64 and powerpc64le on a POWER9 system.

Reviewed by: PowerPC, jhibbits, jhb
Differential Revision: https://reviews.freebsd.org/D41837