ARM: dts: imx6: phyFLEX: Fix UART hardware flow control

Serial interface uart3 on phyFLEX board is capable of 5-wire connection
including signals RTS and CTS for hardware flow control.

Fix signals UART3_CTS_B and UART3_RTS_B padmux assignments and add
missing property "uart-has-rtscts" to allow serial interface to be
configured and used with the hardware flow control.

Signed-off-by: Primoz Fiser <[e-mail]>
Signed-off-by: Shawn Guo <[e-mail]>

arch/arm/boot/dts/imx6qdl-phytec-pfla02.dtsi

···
 			fsl,pins = <
 				MX6QDL_PAD_EIM_D24__UART3_TX_DATA	0x1b0b1
 				MX6QDL_PAD_EIM_D25__UART3_RX_DATA	0x1b0b1
-				MX6QDL_PAD_EIM_D30__UART3_RTS_B		0x1b0b1
-				MX6QDL_PAD_EIM_D31__UART3_CTS_B		0x1b0b1
+				MX6QDL_PAD_EIM_D31__UART3_RTS_B		0x1b0b1
+				MX6QDL_PAD_EIM_D30__UART3_CTS_B		0x1b0b1
 			>;
 		};
 
···
 &uart3 {
 	pinctrl-names = "default";
 	pinctrl-0 = <&pinctrl_uart3>;
+	uart-has-rtscts;
 	status = "disabled";
 };