Fix a regression introduced in r336439.
Rather than allowing any linked list of algorithms, allow at most two
(typically, some combination of encrypt and/or MAC). Removes a WAITOK
malloc in an unsleepable context (classic LOR) by placing both software
algorithm contexts within the OCF-managed session object.
Tested with 'cryptocheck -a all -d cryptosoft0', which includes some
encrypt-and-MAC modes.
PR: 230304
Reported by: sef@
9ebbebe4f7