clocksource/drivers/owl: Improve owl_timer_init fail messages

Check the return from clocksource_mmio_init, add messages in case of
an error and in case of not having a defined clock property.

Signed-off-by: Matheus Castello <matheus@castello.eng.br>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/20200219004810.411190-1-matheus@castello.eng.br

drivers/clocksource/timer-owl.c

@@ -135,17 +135,24 @@ static int __init owl_timer_init(struct device_node *node)
 	}
 
 	clk = of_clk_get(node, 0);
-	if (IS_ERR(clk))
-		return PTR_ERR(clk);
+	if (IS_ERR(clk)) {
+		ret = PTR_ERR(clk);
+		pr_err("Failed to get clock for clocksource (%d)\n", ret);
+		return ret;
+	}
 
 	rate = clk_get_rate(clk);
 
 	owl_timer_reset(owl_clksrc_base);
 	owl_timer_set_enabled(owl_clksrc_base, true);
 
 	sched_clock_register(owl_timer_sched_read, 32, rate);
-	clocksource_mmio_init(owl_clksrc_base + OWL_Tx_VAL, node->name,
-			      rate, 200, 32, clocksource_mmio_readl_up);
+	ret = clocksource_mmio_init(owl_clksrc_base + OWL_Tx_VAL, node->name,
+				    rate, 200, 32, clocksource_mmio_readl_up);
+	if (ret) {
+		pr_err("Failed to register clocksource (%d)\n", ret);
+		return ret;
+	}
 
 	owl_timer_reset(owl_clkevt_base);