drivers/rtc/rtc-s5m.c: re-add support for devices without irq specified

The rtc-s5m driver used to support devices without irq specified in the
past. Re-add this support.

The patch fixes boot for Insignal's Exynos4412 based Origen board.

Error messages before the patch:

...
Unable to handle kernel NULL pointer dereference at virtual address 00000094
pgd = c0004000
[00000094] *pgd=00000000
Internal error: Oops: 5 [#1] PREEMPT SMP ARM
Modules linked in:
CPU: 1 PID: 1 Comm: swapper/0 Not tainted 3.16.0-next-20140804-00008-ga59480f-dirty #701
task: ea80f000 ti: ea882000 task.ti: ea882000
PC is at regmap_irq_get_virq+0x0/0x28
LR is at s5m_rtc_probe+0xdc/0x310
pc : [<c02574fc>] lr : [<c02de75c>] psr: 80000153
sp : ea883e48 ip : 00000000 fp : 00000000
r10: 0000000c r9 : c05de7ac r8 : eaabc600
r7 : eaa6b4d0 r6 : c0439e8c r5 : eaabc610 r4 : eab30e50
r3 : 00000000 r2 : 00000000 r1 : 0000000c r0 : 00000000
Flags: Nzcv IRQs on FIQs off Mode SVC_32 ISA ARM Segment kernel
Control: 10c5387d Table: 4000404a DAC: 00000015
Process swapper/0 (pid: 1, stack limit = 0xea882240)
Backtrace:
regmap_irq_get_virq
s5m_rtc_probe
platform_drv_probe
driver_probe_device
__driver_attach
bus_for_each_dev
bus_add_driver
driver_register
do_one_initcall
kernel_init_freeable
kernel_init
---[ end trace a954d7f019122700 ]---
Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b
...

Signed-off-by: Bartlomiej Zolnierkiewicz <[e-mail]>
Reviewed-by: Krzysztof Kozlowski <[e-mail]>
Tested-by: Krzysztof Kozlowski <[e-mail]>
Acked-by: Kyungmin Park <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

drivers/rtc/rtc-s5m.c

···
 	info->device_type = s5m87xx->device_type;
 	info->wtsr_smpl = s5m87xx->wtsr_smpl;
 
-	info->irq = regmap_irq_get_virq(s5m87xx->irq_data, alarm_irq);
-	if (info->irq <= 0) {
-		ret = -EINVAL;
-		dev_err(&pdev->dev, "Failed to get virtual IRQ %d\n",
+	if (s5m87xx->irq_data) {
+		info->irq = regmap_irq_get_virq(s5m87xx->irq_data, alarm_irq);
+		if (info->irq <= 0) {
+			ret = -EINVAL;
+			dev_err(&pdev->dev, "Failed to get virtual IRQ %d\n",
 				alarm_irq);
-		goto err;
+			goto err;
+		}
 	}
 
 	platform_set_drvdata(pdev, info);
···
 	if (IS_ERR(info->rtc_dev)) {
 		ret = PTR_ERR(info->rtc_dev);
 		goto err;
+	}
+
+	if (!info->irq) {
+		dev_info(&pdev->dev, "Alarm IRQ not available\n");
+		return 0;
 	}
 
 	ret = devm_request_threaded_irq(&pdev->dev, info->irq, NULL,
···
 	struct s5m_rtc_info *info = dev_get_drvdata(dev);
 	int ret = 0;
 
-	if (device_may_wakeup(dev))
+	if (info->irq && device_may_wakeup(dev))
 		ret = disable_irq_wake(info->irq);
 
 	return ret;
···
 	struct s5m_rtc_info *info = dev_get_drvdata(dev);
 	int ret = 0;
 
-	if (device_may_wakeup(dev))
+	if (info->irq && device_may_wakeup(dev))
 		ret = enable_irq_wake(info->irq);
 
 	return ret;