clocksource: asm9260: Fix of_io_request_and_map error check

of_io_request_and map returns an error pointer, but the current code assumes
that on error the returned pointer will be NULL.

Obviously, that makes the check completely useless. Change the test to actually
check for the proper error code.
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: http://lkml.kernel.org/r/1430579006-32702-4-git-send-email-maxime.ripard@free-electrons.comSigned-off-by: Thomas Gleixner <tglx@linutronix.de>

drivers/clocksource/asm9260_timer.c

@@ -178,7 +178,7 @@ static void __init asm9260_timer_init(struct device_node *np)
 	unsigned long rate;
 
 	priv.base = of_io_request_and_map(np, 0, np->name);
-	if (!priv.base)
+	if (IS_ERR(priv.base))
 		panic("%s: unable to map resource", np->name);
 
 	clk = of_clk_get(np, 0);