hs: Use AES256 prop224 descriptors
Support got added recently so use it in hs_descriptor.c instead of AES128. Proposal 224 has been updated to use aes256.
* Instantiate STREAM with AES256-CTR.Support got added recently so use it in hs_descriptor.c instead of AES128. Proposal 224 has been updated to use aes256.
* Instantiate STREAM with AES256-CTR.