Works in the usual USB DFU mode, and can program external SPI flash. It
will enable XSPI memory-mapped mode before jumping to the application
firmware in the external SPI flash.
Signed-off-by: Damien George <damien@micropython.org>
No functional change, just code factoring to have the Python bindings in
one location, and all the ports use those same bindings.
Signed-off-by: Damien George <damien@micropython.org>