ARM: dts: stm32: Add DAC pins used on stm32mp157c-ed1

Define pins that can be used by digital-to-analog converter on
stm32mp157c eval daughter board:
- PA4 and PA5 pins are available respectively on JP11 and JP10
Signed-off-by: Fabrice Gasnier <fabrice.gasnier@st.com>
Signed-off-by: Alexandre Torgue <alexandre.torgue@st.com>

arch/arm/boot/dts/stm32mp157-pinctrl.dtsi

@@ -183,6 +183,18 @@ pins {
 				};
 			};
 
+			dac_ch1_pins_a: dac-ch1 {
+				pins {
+					pinmux = <STM32_PINMUX('A', 4, ANALOG)>;
+				};
+			};
+
+			dac_ch2_pins_a: dac-ch2 {
+				pins {
+					pinmux = <STM32_PINMUX('A', 5, ANALOG)>;
+				};
+			};
+
 			dcmi_pins_a: dcmi-0 {
 				pins {
 					pinmux = <STM32_PINMUX('H', 8,  AF13)>,/* DCMI_HSYNC */