CONFIG_CRYPTO_MD5_PPC is not available for the selected architecture x86.
Result is shown for architecture powerpc

Digests: MD5

modulename: md5-ppc.ko

configname: CONFIG_CRYPTO_MD5_PPC

Linux Kernel Configuration
└─>Accelerated Cryptographic Algorithms for CPU (powerpc)
└─>Digests: MD5
In linux kernel since version 3.10 (release Date: 2013-06-30)
MD5 message digest algorithm (RFC1321)

Architecture: powerpc
source code:
/arch/powerpc/crypto/

depends
CONFIG_PPC