The 2350 doesn't have a boot2 like the 2040, but it does have the
concept of a xip setup function that could be customized. By default the
bootrom searches for the attached flash chip and provides an xip setup
func at the base of the bootram. That bootram is not executable, so it
still needs to be copied to ram like boot2 would be.
Currently does not use inline assembly.
Also switch to picotool, as elf2uf2 has not been patched to support the
2350.
