nRF52: clean pwm structures on deinit

targets/TARGET_NORDIC/TARGET_NRF5x/TARGET_NRF52/pinmap_ex.c

@@ -369,6 +369,27 @@ int pin_instance_pwm(PinName pwm)
     return instance;
 }
 
+/**
+ * Brief       Find hardware instance for the provided PWM pin and free it
+ *
+ * Parameter   pwm   pwm pin.
+ *
+ * Return      Nothing
+ */
+void pin_instance_pwm_free(PinName pwm)
+{
+    /* Search dynamic map for entry. */
+    for (size_t index = 0; index < NORDIC_PWM_COUNT; index++) {
+
+        /* Pins match previous dynamic allocation, return instance. */
+        if (nordic_internal_pwm[index] == pwm) {
+
+            nordic_internal_pwm[index] = NC;
+            break;
+        }
+    }
+}
+
 
 /***
  *      _    _         _____ _______

targets/TARGET_NORDIC/TARGET_NRF5x/TARGET_NRF52/pinmap_ex.h

@@ -120,6 +120,15 @@ int pin_instance_spi(PinName mosi, PinName miso, PinName clk);
  */
 int pin_instance_pwm(PinName pwm);
 
+/**
+ * Brief       Find hardware instance for the provided PWM pin and free it
+ *
+ * Parameter   pwm   pwm pin.
+ *
+ * Return      Nothing
+ */
+void pin_instance_pwm_free(PinName pwm);
+
 /**
  * @brief      Find hardware instance for the provided UART pins.
  *

targets/TARGET_NORDIC/TARGET_NRF5x/TARGET_NRF52/pwmout_api.c

@@ -173,6 +173,9 @@ void pwmout_free(pwmout_t *obj)
 
     MBED_ASSERT(obj);
 
+    /* Also deinit the undelying PinMap_PWM entry */
+    pin_instance_pwm_free(obj->pin);
+
     /* Uninitialize PWM instance. */
     nrfx_pwm_uninit(&nordic_nrf5_pwm_instance[obj->instance]);
 }