avalon2 & littlefury: Use shared crc16 logic
avalon2: Make use of 2D work manager to avoid overlapping with other miner work
configure: Fix avalon2
configure: Build work2d code for avalon2
avalon2: Rename avalon2 driver to avoid digits in name (AV2 -> AVD)
avalon2: Always use pdiff 1 for shares
avalon2: Fix usage with fewer than 3 modules