This unifies the flash config to the settings used by the Boot ROM.
This makes the config unique per board which allows for changing
quad enable and status bit differences per flash device. It also
allows for timing differences due to the board layout.
This change also tweaks linker layout to leave more ram space for
the CircuitPython heap.
This started while adding USB MIDI support (and descriptor support is
in this change.) When seeing that I'd have to implement the MIDI class
logic twice, once for atmel-samd and once for nrf, I decided to refactor
the USB stack so its shared across ports. This has led to a number of
changes that remove items from the ports folder and move them into
supervisor.
Furthermore, we had external SPI flash support for nrf pending so I
factored out the connection between the usb stack and the flash API as
well. This PR also includes the QSPI support for nRF.
Scott Shawcroft
Jeff Epler