ARM: at91: pm: fallback to slowclock when backup mode fails

If the backup sram allocation fails, ensure we can suspend by falling back
to the usual slow clock mode.

Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Acked-by: Wenyou Yang <wenyou.yang@atmel.com>

arch/arm/mach-at91/pm.c

@@ -544,6 +544,11 @@ static void __init at91_pm_backup_init(void)
 securam_fail:
 	iounmap(pm_data.sfrbu);
 	pm_data.sfrbu = NULL;
+
+	if (pm_data.standby_mode == AT91_PM_BACKUP)
+		pm_data.standby_mode = AT91_PM_SLOW_CLOCK;
+	if (pm_data.suspend_mode == AT91_PM_BACKUP)
+		pm_data.suspend_mode = AT91_PM_SLOW_CLOCK;
 }
 
 struct pmc_info {