feat(cherryusb): add cherryusb library

[sakumisu]

Support usb device and host with cherryusb. Also host hub supports.

[lurch]

Stupid question 1: Why does this modify the linker files in src/rp2_common/pico_crt0/rp2040/ but not those in src/rp2_common/pico_crt0/rp2350/ ?

Stupid question 2: Can this be used as a complete replacement for TinyUSB? (or would that require a much larger refactoring of the SDK's existing USB code?)

[sakumisu]

Stupid question 1: Why does this modify the linker files in src/rp2_common/pico_crt0/rp2040/ but not those in src/rp2_common/pico_crt0/rp2350/ ?

Stupid question 2: Can this be used as a complete replacement for TinyUSB? (or would that require a much larger refactoring of the SDK's existing USB code?)

1, my mistake, fixed
2, Our transfer api only has write & read and no need loop, it is easy to refactor.

[sakumisu]

Could you list or point out which usb code? I can help to match with cherryusb.

[lurch]

Could you list or point out which usb code? I can help to match with cherryusb.

I did a git grep -i tinyusb and it looks like apart from the src/rp2_common/tinyusb/ directory, tinyusb is only used in src/rp2_common/pico_stdio_usb/ (so perhaps not as much refactoring as I previously thought).

[sakumisu]

Could you list or point out which usb code? I can help to match with cherryusb.

I did a git grep -i tinyusb and it looks like apart from the src/rp2_common/tinyusb/ directory, tinyusb is only used in src/rp2_common/pico_stdio_usb/ (so perhaps not as much refactoring as I previously thought).

done