boards: stm32: Fix incomplete nodes descriptions

Now that pinctrl-0 property is required in descriptions of nodes
that implies definition of pins, these incomplete nodes definitions
lead to build error.
Fix or remove depending of the board documentation.

Signed-off-by: Erwan Gouriou <[email protected]>

Author: erwango

boards/arm/nucleo_l496zg/nucleo_l496zg.dts

@@ -91,6 +91,8 @@
 };
 
 &usart3 {
+	pinctrl-0 = <&usart3_tx_pd8 &usart3_rx_pd9>;
+	pinctrl-names = "default";
 	current-speed = <115200>;
 	status = "okay";
 };

boards/arm/sensortile_box/sensortile_box.dts

@@ -176,14 +176,6 @@ zephyr_udc0: &usbotg_fs {
 	status = "okay";
 };
 
-&timers2 {
-	status = "okay";
-
-	pwm {
-		status = "okay";
-	};
-};
-
 &rtc {
 	status = "okay";
 };