ARM: dts: meson8b: add the I2C_A, PWM_C and UART_B pins

These are used for example on the Endless Mini (EC-100):
- I2C_A is connected to the Realtek RT5640 audio codec
- PWM_C (GPIODV_9) is connected to a PWM regulator which is used for
  VCCK (CPU voltage supply)
- UART_B is connected to the Bluetooth module (of the RTL8723BS SDIO
  wifi and Bluetooth combo chip)
Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Signed-off-by: Kevin Hilman <khilman@baylibre.com>

arch/arm/boot/dts/meson8b.dtsi

@@ -223,6 +223,13 @@ mux {
 			};
 		};
 
+		i2c_a_pins: i2c-a {
+			mux {
+				groups = "i2c_sda_a", "i2c_sck_a";
+				function = "i2c_a";
+			};
+		};
+
 		sd_b_pins: sd-b {
 			mux {
 				groups = "sd_d0_b", "sd_d1_b", "sd_d2_b",
@@ -230,6 +237,29 @@ mux {
 				function = "sd_b";
 			};
 		};
+
+		pwm_c1_pins: pwm-c1 {
+			mux {
+				groups = "pwm_c1";
+				function = "pwm_c";
+			};
+		};
+
+		uart_b0_pins: uart-b0 {
+			mux {
+				groups = "uart_tx_b0",
+				       "uart_rx_b0";
+				function = "uart_b";
+			};
+		};
+
+		uart_b0_cts_rts_pins: uart-b0-cts-rts {
+			mux {
+				groups = "uart_cts_b0",
+				       "uart_rts_b0";
+				function = "uart_b";
+			};
+		};
 	};
 };