Make irq init function a weak function

git-svn-id: svn://svn.code.sf.net/p/nuttx/code/trunk@3031 42af7a65-404d-4744-a932-0658087f49c3

arch/avr/src/at91uc3/at91uc3_internal.h

@@ -277,7 +277,7 @@ EXTERN bool at91uc3_gpioread(uint16_t pinset);
  ****************************************************************************/
 
 #ifdef CONFIG_AVR32_GPIOIRQ
-EXTERN void gpio_irqinitialize(void);
+EXTERN void weak_function gpio_irqinitialize(void);
 #endif
 
 /****************************************************************************

arch/avr/src/at91uc3/at91uc3_irq.c

@@ -230,7 +230,12 @@ void up_irqinitialize(void)
   /* Initialize GPIO interrupt facilities */
 
 #ifdef CONFIG_AVR32_GPIOIRQ
-  gpio_irqinitialize();
+#ifdef CONFIG_HAVE_WEAKFUNCTIONS
+  if (gpio_irqinitialize != NULL)
+#endif
+    {
+      gpio_irqinitialize();
+    }
 #endif
 
   /* And finally, enable interrupts */