ARM: dts: stm32: Add alternate pinmux for SAI2 pins on stm32mp15

Add new mux option for SAI2 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

@@ -1028,6 +1028,25 @@ pins {
 		};
 	};
 
+	sai2a_pins_c: sai2a-4 {
+		pins {
+			pinmux = <STM32_PINMUX('D', 13, AF10)>, /* SAI2_SCK_A */
+				 <STM32_PINMUX('D', 11, AF10)>, /* SAI2_SD_A */
+				 <STM32_PINMUX('D', 12, AF10)>; /* SAI2_FS_A */
+			slew-rate = <0>;
+			drive-push-pull;
+			bias-disable;
+		};
+	};
+
+	sai2a_sleep_pins_c: sai2a-5 {
+		pins {
+			pinmux = <STM32_PINMUX('D', 13, ANALOG)>, /* SAI2_SCK_A */
+				 <STM32_PINMUX('D', 11, ANALOG)>, /* SAI2_SD_A */
+				 <STM32_PINMUX('D', 12, ANALOG)>; /* SAI2_FS_A */
+		};
+	};
+
 	sai2b_pins_a: sai2b-0 {
 		pins1 {
 			pinmux = <STM32_PINMUX('E', 12, AF10)>, /* SAI2_SCK_B */
@@ -1065,6 +1084,19 @@ pins {
 		};
 	};
 
+	sai2b_pins_c: sai2a-4 {
+		pins1 {
+			pinmux = <STM32_PINMUX('F', 11, AF10)>; /* SAI2_SD_B */
+			bias-disable;
+		};
+	};
+
+	sai2b_sleep_pins_c: sai2a-sleep-5 {
+		pins {
+			pinmux = <STM32_PINMUX('F', 11, ANALOG)>; /* SAI2_SD_B */
+		};
+	};
+
 	sai4a_pins_a: sai4a-0 {
 		pins {
 			pinmux = <STM32_PINMUX('B', 5, AF10)>; /* SAI4_SD_A */