ARM: dts: sun8i: r40: Add pinmux settings for UART3 on PG pingroup

UART3 on the PG pingroup on the R40 SoC is commonly used to connect the
bluetooth controller in a WiFi+Bluetooth combo chip, with the WiFi bits
also on the PG pingroup.

This patch adds two device nodes for UART3 on PG pingroup, one for the
RX/TX pins, and one for the RTS/CTS pins. Consumers can reference either
just the RX/TX pinmux setting or both, depending on the application.
Signed-off-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>

arch/arm/boot/dts/sun8i-r40.dtsi

@@ -389,6 +389,16 @@ uart0_pb_pins: uart0-pb-pins {
 				pins = "PB22", "PB23";
 				function = "uart0";
 			};
+
+			uart3_pg_pins: uart3-pg-pins {
+				pins = "PG6", "PG7";
+				function = "uart3";
+			};
+
+			uart3_rts_cts_pg_pins: uart3-rts-cts-pg-pins {
+				pins = "PG8", "PG9";
+				function = "uart3";
+			};
 		};
 
 		wdt: watchdog@1c20c90 {