kernel: build crypto md5/sha1/sha256 modules for powerpc

kernel: build crypto md5/sha1/sha256 modules for powerpc

This builds and enables kernel optimized modules for mpc85xx target:
- CONFIG_CRYPTO_MD5_PPC [1]
- CONFIG_CRYPTO_SHA1_PPC_SPE [2]
- CONFIG_CRYPTO_SHA256_PPC_SPE [3]

Where it was possible, then use Signal Processing Engine, because
CONFIG_SPE is already enabled in mpc85xx config.

[1] https://cateee.net/lkddb/web-lkddb/CRYPTO_MD5_PPC.html
[2] https://cateee.net/lkddb/web-lkddb/CRYPTO_SHA1_PPC.html
[3] https://cateee.net/lkddb/web-lkddb/CRYPTO_SHA256_PPC_SPE.html

Signed-off-by: Josef Schlehofer <pepe.schlehofer@gmail.com>