arm64: dts: allwinner: a64: Add UART2 pin nodes

UART2 is exposed on the Pi connector of Pine64. Make a pinctrl node
available at the SoC level, to simplify enabling UART2 via DT overlay.
Signed-off-by: Andreas Färber <afaerber@suse.de>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>

arch/arm64/boot/dts/allwinner/sun50i-a64.dtsi

@@ -317,6 +317,11 @@ uart1_rts_cts_pins: uart1_rts_cts_pins {
 				pins = "PG8", "PG9";
 				function = "uart1";
 			};
+
+			uart2_pins: uart2-pins {
+				pins = "PB0", "PB1";
+				function = "uart2";
+			};
 		};
 
 		uart0: serial@1c28000 {