Merge tag 'usb-serial-5.14-rc1' of into usb-next

Johan writes:

USB-serial updates for 5.14-rc1

Here are the USB-serial updates for 5.14-rc1, including:

 - gpio support for CP2108
 - chars_in_buffer and write_room return-value updates
 - chars_in_buffer and write_room clean ups

Included are also various clean ups.

All have been in linux-next with no reported issues.

* tag 'usb-serial-5.14-rc1' of
  USB: serial: cp210x: add support for GPIOs on CP2108
  USB: serial: drop irq-flags initialisations
  USB: serial: mos7840: drop buffer-callback return-value comments
  USB: serial: mos7720: drop buffer-callback sanity checks
  USB: serial: io_edgeport: drop buffer-callback sanity checks
  USB: serial: digi_acceleport: add chars_in_buffer locking
  USB: serial: digi_acceleport: reduce chars_in_buffer over-reporting
  USB: serial: make usb_serial_driver::chars_in_buffer return uint
  USB: serial: make usb_serial_driver::write_room return uint