py/mphal.h contains declarations for generic mp_hal_XXX functions, such
as stdio and delay/ticks, which ports should provide definitions for. A
port will also provide mphalport.h with further HAL declarations.
This fix adds PIDs 9801 and 9802 to the pybcdc.inf file.
When in CDC only mode, it presents itself as a Communcations
device rather than as a composite device. Presenting as a
composite device with only the CDC interface seems to confuse
windows.
To test and make sure that the correct pybcdc.inf was being used,
I used USBDeview from http://www.nirsoft.net/utils/usb_devices_view.html
to uninstall any old pyboard drivers (Use Control-F and search
for pyboard). I found running USBDeview as administrator worked best.
Installing the driver in CDC+MSC mode first is recommended (since the
pybcdc.inf file in on the internal flash drive). Then when you switch
modes everything seems to work properly.
I used https://github.com/dhylands/upy-examples/blob/master/boot_switch.py
to easily switch the pyboard between the various USB modes for testing.
