Adds a shim layer around the imx uart driver to adapt it to the Zephyr
serial interface.
Modem mode was introduce to control it as DCE and DTE and can be
configured in the device tree:
modem-mode:
type: int
category: required
description: Set the UART Port to modem mode 0 (dce) 1 (dte)
generation: define
For now only the UART 2 was tested.
Signed-off-by: Diego Sueiro <diego.sueiro@gmail.com>