clocksource: clksrc-of: Warn if no clock sources are found

Many platforms rely on clocksource_of_init() being implicitly
called for registering clock sources and will get zero warnings
if no working clock source is available. Let's print a critical
error message if no clock source is found.
Acked-by: NLee Jones <lee.jones@linaro.org>
Signed-off-by: NLinus Walleij <linus.walleij@linaro.org>
Signed-off-by: NDaniel Lezcano <daniel.lezcano@linaro.org>

drivers/clocksource/clksrc-of.c

@@ -28,6 +28,7 @@ void __init clocksource_of_init(void)
 	struct device_node *np;
 	const struct of_device_id *match;
 	clocksource_of_init_fn init_func;
+	unsigned clocksources = 0;
 
 	for_each_matching_node_and_match(np, __clksrc_of_table, &match) {
 		if (!of_device_is_available(np))
@@ -36,5 +37,8 @@ void __init clocksource_of_init(void)
 		init_func = match->data;
 		init_func(np);
 		of_node_put(np);
+		clocksources++;
 	}
+	if (!clocksources)
+		pr_crit("%s: no matching clocksources found\n", __func__);
 }