IAR generates warning Pe111 'statement is unreachable'. In a couple of
cases, replace return statements with TU_ATTR_FALLTHROUGH; because some
compilers apparently can't figure out that the return statements are
unreachable but do whinge about an imagined fall-through without them!
* Removed some compiler warnings, and cleaned out unnecessary warning suppression from CMake suppress_tinyusb_warnings()
* Made explicit family_configure_dual_usb_example() for DUAL mode examples as family_configure_target() may not generally be called multiple times for the same target
* Renamed library pico_pio_usb to tinyusb_picio_pio_usb to be clearer and avoid conflict if someone already has a pico_pio_usb in their project
* Added family_add_pico_pio_usb() method for adding Pico-PIO_SUB support to an existing example
* Allowed tinyusb_pico_pio_usb to be added to regular apps using the Pico SDK
