Clearing interrupt flag before setting interrupt

Author: Troels51

cpu/samd21/periph/gpio.c

@@ -468,6 +468,7 @@ int gpio_init_int(gpio_t dev, gpio_pp_t pullup, gpio_flank_t flank, gpio_cb_t cb
     gpio_config[extint].arg = arg;
 
     /*Enable pin interrupt */
+    EIC->INTFLAG.reg |= (1 << extint);
     EIC->INTENSET.reg = 1 << extint;
     EIC->WAKEUP.reg |= 1 << extint;