ARM: dts: stm32: add pwm sleep pin muxing for stm32mp157c-ev1

Add PWM pinctrl definitions used in low-power (sleep) mode on
stm32mp157c-ev1.
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

@@ -596,6 +596,12 @@ pins {
 				};
 			};
 
+			pwm2_sleep_pins_a: pwm2-sleep-0 {
+				pins {
+					pinmux = <STM32_PINMUX('A', 3, ANALOG)>; /* TIM2_CH4 */
+				};
+			};
+
 			pwm8_pins_a: pwm8-0 {
 				pins {
 					pinmux = <STM32_PINMUX('I', 2, AF3)>; /* TIM8_CH4 */
@@ -605,6 +611,12 @@ pins {
 				};
 			};
 
+			pwm8_sleep_pins_a: pwm8-sleep-0 {
+				pins {
+					pinmux = <STM32_PINMUX('I', 2, ANALOG)>; /* TIM8_CH4 */
+				};
+			};
+
 			pwm12_pins_a: pwm12-0 {
 				pins {
 					pinmux = <STM32_PINMUX('H', 6, AF2)>; /* TIM12_CH1 */
@@ -614,6 +626,12 @@ pins {
 				};
 			};
 
+			pwm12_sleep_pins_a: pwm12-sleep-0 {
+				pins {
+					pinmux = <STM32_PINMUX('H', 6, ANALOG)>; /* TIM12_CH1 */
+				};
+			};
+
 			qspi_clk_pins_a: qspi-clk-0 {
 				pins {
 					pinmux = <STM32_PINMUX('F', 10, AF9)>; /* QSPI_CLK */