default or selected kernelversion does not have config value CONFIG_CRYPTO_MORUS640.
Result is shown for kernelversion 6.9.9

MORUS-640 AEAD algorithm

modulename: morus640.ko

configname: CONFIG_CRYPTO_MORUS640

Linux Kernel Configuration
└─>Cryptographic API
└─>MORUS-640 AEAD algorithm
In linux kernel since version 4.2 (release Date: 2015-08-30)  
Support for the MORUS-640 dedicated AEAD algorithm.

source code:
crypto/morus640.c

depends
CONFIG_CRYPTO