gc3355: Refactor to remove SHA2 code specific to the 5-Chip GridSeed Orb

Code was not completed or functional and unlikely to be completed
Does not affect DualMiner ASICs
Merge pull request #491 from nwoolls/task/gridseed-remove-sha2

gc3355: Refactor to remove SHA2 code specific to the 5-Chip GridSeed Orb