ARM: at91/at91sam9x5.dtsi: fix usart3 TXD

Comment for usart3 TXD (TXD3) is correct, dt code is wrong.
Signed-off-by: NDouglas Gilbert <dgilbert@interlog.com>
Signed-off-by: NNicolas Ferre <nicolas.ferre@atmel.com>

arch/arm/boot/dts/at91sam9x5.dtsi

@@ -199,7 +199,7 @@
 				usart3 {
 					pinctrl_usart3: usart3-0 {
 						atmel,pins =
-							<2 23 0x2 0x1	/* PC22 periph B with pullup */
+							<2 22 0x2 0x1	/* PC22 periph B with pullup */
 							 2 23 0x2 0x0>;	/* PC23 periph B */
 					};