ARM: dts: stm32: Add alternate pinmux for ADC pins

Add another mux option for ADC pins, this is used on AV96 board.
Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Alexandre Torgue <alexandre.torgue@st.com>
Cc: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Cc: Maxime Coquelin <mcoquelin.stm32@gmail.com>
Cc: Patrice Chotard <patrice.chotard@st.com>
Cc: Patrick Delaunay <patrick.delaunay@st.com>
Cc: linux-stm32@st-md-mailman.stormreply.com
To: linux-arm-kernel@lists.infradead.org
Signed-off-by: Alexandre Torgue <alexandre.torgue@st.com>

arch/arm/boot/dts/stm32mp15-pinctrl.dtsi

@@ -21,6 +21,13 @@ pins {
 		};
 	};
 
+	adc12_ain_pins_b: adc12-ain-1 {
+		pins {
+			pinmux = <STM32_PINMUX('F', 12, ANALOG)>, /* ADC1 in6 */
+				 <STM32_PINMUX('F', 13, ANALOG)>; /* ADC2 in2 */
+		};
+	};
+
 	adc12_usb_cc_pins_a: adc12-usb-cc-pins-0 {
 		pins {
 			pinmux = <STM32_PINMUX('A', 4, ANALOG)>, /* ADC12 in18 */