AVR32: fix timer_init() function

timer_init() now returns an int (the error code) instead of void.
This makes compilation fail with:

interrupts.c:111: error: conflicting types for 'timer_init'
/home/svens/u-boot/u-boot/include/common.h:246: error: previous
declaration of 'timer_init' was here
make[1]: *** [interrupts.o] Error 1

Signed-off-by: Sven Schnelle <svens@stackframe.org>
Acked-by: Andreas Bießmann <andreas.devel@googlemail.com>
Signed-off-by: Anatolij Gustschin <agust@denx.de>

arch/avr32/cpu/interrupts.c

@@ -107,7 +107,7 @@ static int set_interrupt_handler(unsigned int nr, void (*handler)(void),
 	return 0;
 }
 
-void timer_init(void)
+int timer_init(void)
 {
 	extern void timer_interrupt_handler(void);
 	u64 tmp;
@@ -120,8 +120,9 @@ void timer_init(void)
 	tb_factor = (u32)tmp;
 
 	if (set_interrupt_handler(0, &timer_interrupt_handler, 3))
-		return;
+		return -EINVAL;
 
 	/* For all practical purposes, this gives us an overflow interrupt */
 	sysreg_write(COMPARE, 0xffffffff);
+	return 0;
 }