Make RPC methods public
firmware: Update Max3421e ports to use new board
firmware: Clear flash select

The flash module hasn't been implemented yet.
rpc_test: Add newline
rpc_test: Do not invert the null terminator
firmware: Set SPI SS pin mode after clearing them

Otherwise the SS bit will be low (active) as soon as the pin is set to an
output.
fatfs: set fast SPI clock even if initialization failed

The default setting should be a fast clock.
firmware: Allow reading from Core
firmware: Support file reads that partially fill buffer
Expose the RPC module in DuinoCube API
examples: Read Core ID from coprocessor