Fix requested in arduino#155 for PMW on pin 13

Author: agdl

variants/arduino_zero/variant.cpp

@@ -134,7 +134,7 @@ const PinDescription g_APinDescription[]=
   { PORTA, 19, PIO_TIMER_ALT, (PIN_ATTR_DIGITAL|PIN_ATTR_PWM|PIN_ATTR_TIMER_ALT), No_ADC_Channel, PWM0_CH3, TCC0_CH3, EXTERNAL_INT_3 }, // TCC0/WO[3]
 
   // 13 (LED)
-  { PORTA, 17, PIO_PWM, (PIN_ATTR_DIGITAL|PIN_ATTR_PWM), No_ADC_Channel, PWM2_CH1, NOT_ON_TIMER, EXTERNAL_INT_1 }, // TCC2/WO[1]
+  { PORTA, 17, PIO_PWM, (PIN_ATTR_DIGITAL|PIN_ATTR_PWM|PIN_ATTR_TIMER), No_ADC_Channel, PWM2_CH1, TCC2_CH1, EXTERNAL_INT_1 }, // TCC2/WO[1]
 
   // 14..19 - Analog pins
   // --------------------