clocksource/drivers/asm9260: Add a check for of_clk_get

asm9260_timer_init misses a check for of_clk_get.
Add a check for it and print errors like other clocksource drivers.
Signed-off-by: Chuhong Yuan <hslester96@gmail.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/20191016124330.22211-1-hslester96@gmail.com

drivers/clocksource/asm9260_timer.c

@@ -194,6 +194,10 @@ static int __init asm9260_timer_init(struct device_node *np)
 	}
 
 	clk = of_clk_get(np, 0);
+	if (IS_ERR(clk)) {
+		pr_err("Failed to get clk!\n");
+		return PTR_ERR(clk);
+	}
 
 	ret = clk_prepare_enable(clk);
 	if (ret) {