ARM: pxa: fix build issue while CONFIG_OF is disabled

arch/arm/mach-pxa/built-in.o: In function `pxa3xx_dt_init_irq':
saar.c:(.init.text+0x604): undefined reference to `pxa_dt_irq_init'
Signed-off-by: Haojian Zhuang <haojian.zhuang@gmail.com>

arch/arm/mach-pxa/pxa3xx.c

@@ -402,11 +402,13 @@ void __init pxa3xx_init_irq(void)
 	pxa_init_irq(56, pxa3xx_set_wake);
 }
 
+#ifdef CONFIG_OF
 void __init pxa3xx_dt_init_irq(void)
 {
 	__pxa3xx_init_irq();
 	pxa_dt_irq_init(pxa3xx_set_wake);
 }
+#endif	/* CONFIG_OF */
 
 static struct map_desc pxa3xx_io_desc[] __initdata = {
 	{	/* Mem Ctl */