Fix BatteryChargerInterrupt compilation error (arduino-libraries#21)

Fix BatteryChargerInterrupt compilation error on gsm, nb and 1010

Author: Rocketct

examples/BatteryChargerInterrupt/BatteryChargerInterrupt.ino

@@ -23,8 +23,11 @@ void setup() {
     ; // wait for serial port to connect. Needed for native USB port only
   }
 
+// Available only for MKRGSM1400 and MKRNB1500
+#if defined(ARDUINO_SAMD_MKRGSM1400) || defined(ARDUINO_SAMD_MKRNB1500)
   // Attach the PMIC IRQ pin
   attachInterrupt(digitalPinToInterrupt(PMIC_IRQ_PIN), batteryConnected, FALLING);
+#endif
 
   if (!PMIC.begin()) {
     Serial.println("Failed to initialize PMIC!");
@@ -72,20 +75,16 @@ void loop() {
 
       // loop until charge is done
       if (PMIC.chargeStatus() != CHARGE_TERMINATION_DONE) {
-        Serial.println("Charge mode");
-        Serial.println(PMIC.isCharging());
         delay(1000);
       } else {
         // Disable the charger
-
         Serial.println("Disable Charge mode");
         if (!PMIC.disableCharge()) {
           Serial.println("Error disabling Charge mode");
         }
         // if you really want to detach the battery call
         // PMIC.disableBATFET();
         //isbatteryconnected = false;
-
       }
     }
   }

examples/PMICBoostMode/PMICBoostMode.ino

@@ -15,7 +15,7 @@
 
 #include <Arduino_PMIC.h>
 
-int usb_mode = UNKNOWM_MODE;
+int usb_mode = UNKNOWN_MODE;
 
 void setup()
 {