SPU: Do not pass the midstate to the blades, now that we no longer use it

Also adjust struct padding for proper DMA
SPU: Pass the nonce via a separate field

Also adjust struct padding accordingly
SPU: Control struct padding with a static_assert
PPU: Instead of just verifying the midstate, use it
PPU: Do not pass the midstate to the worker, now that we no longer use it
PPU: Pass the nonce via a separate field