serial: imx: Use generic uart-has-rtscts DT property

Convert the Freescale IMX UART driver from using the vendor-specific
"fsl,uart-has-rtscts" to the generic "uart-has-rtscts" DT property, as
documented by the Generic Serial DT Bindings.

The old vendor-specific property is still recognized by the driver for
backwards compatibility, but deprecated.

Signed-off-by: Geert Uytterhoeven <[e-mail]>
Acked-by: Rob Herring <[e-mail]>
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

Documentation/devicetree/bindings/serial/fsl-imx-uart.txt

···
 - interrupts : Should contain uart interrupt
 
 Optional properties:
-- fsl,uart-has-rtscts : Indicate the uart has rts and cts
+- uart-has-rtscts : Indicate the uart has rts and cts
 - fsl,irda-mode : Indicate the uart supports irda mode
 - fsl,dte-mode : Indicate the uart works in DTE mode. The uart works
                   in DCE mode by default.
···
 	compatible = "fsl,imx51-uart", "fsl,imx21-uart";
 	reg = <0x73fbc000 0x4000>;
 	interrupts = <31>;
-	fsl,uart-has-rtscts;
+	uart-has-rtscts;
 	fsl,dte-mode;
 };

drivers/tty/serial/imx.c

···
 	}
 	sport->port.line = ret;
 
-	if (of_get_property(np, "fsl,uart-has-rtscts", NULL))
+	if (of_get_property(np, "uart-has-rtscts", NULL) ||
+	    of_get_property(np, "fsl,uart-has-rtscts", NULL) /* deprecated */)
 		sport->have_rtscts = 1;
 
 	if (of_get_property(np, "fsl,dte-mode", NULL))