avr32: Fix GPIO initcall breakage

Add essential system devices, including GPIO controllers, automatically
at core_initcall time. This ensures that the devices are there when the
PIO driver gets initialized at postcore_initcall, fixing a bug exposed
by commit d6634db8fe "avr32: Use
platform_driver_probe for pio platform driver".

Signed-off-by: Haavard Skinnemoen <haavard.skinnemoen@atmel.com>

arch/avr32/boards/atstk1000/atstk1004.c

@@ -132,8 +132,6 @@ void __init setup_board(void)
 
 static int __init atstk1004_init(void)
 {
-	at32_add_system_devices();
-
 #ifdef	CONFIG_BOARD_ATSTK100X_SW2_CUSTOM
 	at32_add_device_usart(1);
 #else