serial: imx: Move imx_uart_probe_dt() content into probe()

serial: imx: Move imx_uart_probe_dt() content into probe()

Now that the driver only probes via devicetree, we can move the
content of imx_uart_probe_dt() directly into imx_uart_probe() to
make the code simpler.

Suggested-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Reviewed-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Fabio Estevam <festevam@gmail.com>
Link: https://lore.kernel.org/r/20201209214712.15247-1-festevam@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>