The only thing that's different between all these chips is the flash
size, which can easily be passed as a linker flag instead. This removes
a bunch of duplicate code in an uncommon language (linker script).
I've also fixed a few boards with incorrect flash sizes:
* nano-rp2040 has 16MB instead of 2MB
* macropad-rp2040 has 8MB instead of 2MB
* gopher-badge has 8MB instead of 1MB
This prefix isn't actually used and only adds noise, so remove it.
It may have been useful on Linux that makes a distinction between
/dev/ttyACM* and /dev/ttyUSB* but it isn't now. Also, it's unlikely that
the same vid/pid pair will be shared between an acm and usb driver
anyway.
