CONFIG_CRYPTO_SHA256_ARM is not available for thedefaultarchitecture x86.
Result is shown for architecture arm

SHA-224/256 digest algorithm (ARM-asm and NEON)

modulename: sha256-arm.ko

configname: CONFIG_CRYPTO_SHA256_ARM

Linux Kernel Configuration
└─>ARM Accelerated Cryptographic Algorithms
└─>SHA-224/256 digest algorithm (ARM-asm and NEON)
In linux kernel since version 3.10 (release Date: 2013-06-30)  
SHA-256 secure hash standard (DFIPS 180-2) implemented
using optimized ARM assembler and NEON, when available.

source code: