avr32: Disable the AP7000 internal watchdog on startup

This patch forces the watchdog off in all cases.  That will at least
get rid of the constant reboot cycle, though it won't let the watchdog
actually run in the new kernels:  its probe() comes up with a polite
warning.
Signed-off-by: NHaavard Skinnemoen <haavard.skinnemoen@atmel.com>

cpu/at32ap/cpu.c

@@ -86,6 +86,10 @@ int cpu_init(void)
 	extern void _evba(void);
 	char *p;
 
+	/* in case of soft resets, disable watchdog */
+	sm_writel(WDT_CTRL, SM_BF(KEY, 0x55));
+	sm_writel(WDT_CTRL, SM_BF(KEY, 0xaa));
+
 	gd->cpu_hz = CFG_OSC0_HZ;
 
 	/* TODO: Move somewhere else, but needs to be run before we