HAL: Remove duplication in TARGET_NRF52 gpio_api

Author: hazzlim

targets/TARGET_NORDIC/TARGET_NRF5x/TARGET_NRF52/gpio_api.c

@@ -210,7 +210,6 @@ int gpio_irq_init(gpio_irq_t *obj, PinName pin, gpio_irq_handler handler, uint32
     m_channel_ids[pin] = id;
     obj->ch            = pin;
     m_irq_handler      = handler;
-    m_channel_ids[pin] = id;
 
     gpio_apply_config(pin);
     return 0;