Scratchpad-to-DRAM paging and encryption

[archshift]

This will be a tracking issue for the progress of DRAM encryption in the runtime.

In-memory encryption

• Add AES software implementation into the runtime
• Add support for AES hardware implementations (SBI call for crypto copies?)
• Hook AES driver into memory page in/out
• Use secure IVs for protection against replay attacks

Memory consistency

• Add SHA software software implementation into the runtime
• Add support for SHA hardware implementations
• Store page hashes for consistency checking