samples: servo_motor: Convert to use DEVICE_DT_GET

Replace device_get_binding with DEVICE_DT_GET for getting access
to the pwm controller device.

Signed-off-by: Kumar Gala <kumar.gala@linaro.org>

Author: galak

samples/basic/servo_motor/src/main.c

@@ -17,9 +17,6 @@
 
 #if !DT_NODE_HAS_STATUS(PWM_NODE, okay)
 #error "Unsupported board: pwm-servo devicetree alias is not defined or enabled"
-#define PWM_LABEL ""
-#else
-#define PWM_LABEL DT_LABEL(PWM_NODE)
 #endif
 
 /*
@@ -45,9 +42,9 @@ void main(void)
 
 	printk("Servomotor control\n");
 
-	pwm = device_get_binding(PWM_LABEL);
-	if (!pwm) {
-		printk("Error: didn't find %s device\n", PWM_LABEL);
+	pwm = DEVICE_DT_GET(PWM_NODE);
+	if (!device_is_ready(pwm)) {
+		printk("Error: PWM device %s is not ready\n", pwm->name);
 		return;
 	}