ARM: dts: stm32: add pwm cells to stm32mp157c

STM32 Timers support generic 3 cells PWM to encode PWM number, period and
polarity.

Fixes: 61fc211c ("ARM: dts: stm32: add timers support to stm32mp157c")
Signed-off-by: NFabrice Gasnier <fabrice.gasnier@st.com>
Signed-off-by: NAlexandre Torgue <alexandre.torgue@st.com>

arch/arm/boot/dts/stm32mp157c.dtsi

@@ -139,6 +139,7 @@
 
 			pwm {
 				compatible = "st,stm32-pwm";
+				#pwm-cells = <3>;
 				status = "disabled";
 			};
 
@@ -167,6 +168,7 @@
 
 			pwm {
 				compatible = "st,stm32-pwm";
+				#pwm-cells = <3>;
 				status = "disabled";
 			};
 
@@ -193,6 +195,7 @@
 
 			pwm {
 				compatible = "st,stm32-pwm";
+				#pwm-cells = <3>;
 				status = "disabled";
 			};
 
@@ -221,6 +224,7 @@
 
 			pwm {
 				compatible = "st,stm32-pwm";
+				#pwm-cells = <3>;
 				status = "disabled";
 			};
 
@@ -278,6 +282,7 @@
 
 			pwm {
 				compatible = "st,stm32-pwm";
+				#pwm-cells = <3>;
 				status = "disabled";
 			};
 
@@ -299,6 +304,7 @@
 
 			pwm {
 				compatible = "st,stm32-pwm";
+				#pwm-cells = <3>;
 				status = "disabled";
 			};
 
@@ -320,6 +326,7 @@
 
 			pwm {
 				compatible = "st,stm32-pwm";
+				#pwm-cells = <3>;
 				status = "disabled";
 			};
 
@@ -573,6 +580,7 @@
 
 			pwm {
 				compatible = "st,stm32-pwm";
+				#pwm-cells = <3>;
 				status = "disabled";
 			};
 
@@ -603,6 +611,7 @@
 
 			pwm {
 				compatible = "st,stm32-pwm";
+				#pwm-cells = <3>;
 				status = "disabled";
 			};
 
@@ -676,6 +685,7 @@
 
 			pwm {
 				compatible = "st,stm32-pwm";
+				#pwm-cells = <3>;
 				status = "disabled";
 			};
 
@@ -700,6 +710,7 @@
 
 			pwm {
 				compatible = "st,stm32-pwm";
+				#pwm-cells = <3>;
 				status = "disabled";
 			};
 			timer@15 {
@@ -723,6 +734,7 @@
 
 			pwm {
 				compatible = "st,stm32-pwm";
+				#pwm-cells = <3>;
 				status = "disabled";
 			};