clocksource/drivers/ralink: Convert init function to return error

The init functions do not return any error. They behave as the following:

  - panic, thus leading to a kernel crash while another timer may work and
       make the system boot up correctly

  or

  - print an error and let the caller unaware if the state of the system

Change that by converting the init functions to return an error conforming
to the CLOCKSOURCE_OF_RET prototype.

Proper error handling (rollback, errno value) will be changed later case
by case, thus this change just return back an error or success in the init
function.
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>

arch/mips/ralink/cevt-rt3352.c

@@ -117,11 +117,13 @@ static int systick_set_oneshot(struct clock_event_device *evt)
 	return 0;
 }
 
-static void __init ralink_systick_init(struct device_node *np)
+static int __init ralink_systick_init(struct device_node *np)
 {
+	int ret;
+
 	systick.membase = of_iomap(np, 0);
 	if (!systick.membase)
-		return;
+		return -ENXIO;
 
 	systick_irqaction.name = np->name;
 	systick.dev.name = np->name;
@@ -131,16 +133,21 @@ static void __init ralink_systick_init(struct device_node *np)
 	systick.dev.irq = irq_of_parse_and_map(np, 0);
 	if (!systick.dev.irq) {
 		pr_err("%s: request_irq failed", np->name);
-		return;
+		return -EINVAL;
 	}
 
-	clocksource_mmio_init(systick.membase + SYSTICK_COUNT, np->name,
-			SYSTICK_FREQ, 301, 16, clocksource_mmio_readl_up);
+	ret = clocksource_mmio_init(systick.membase + SYSTICK_COUNT, np->name,
+				    SYSTICK_FREQ, 301, 16,
+				    clocksource_mmio_readl_up);
+	if (ret)
+		return ret;
 
 	clockevents_register_device(&systick.dev);
 
 	pr_info("%s: running - mult: %d, shift: %d\n",
 			np->name, systick.dev.mult, systick.dev.shift);
+
+	return 0;
 }
 
-CLOCKSOURCE_OF_DECLARE(systick, "ralink,cevt-systick", ralink_systick_init);
+CLOCKSOURCE_OF_DECLARE_RET(systick, "ralink,cevt-systick", ralink_systick_init);