ARM: mvebu: fix return value check in armada_xp_pmsu_cpufreq_init()

In case of error, the function clk_get() returns ERR_PTR()
and never returns NULL. The NULL test in the return value
check should be replaced with IS_ERR().
Signed-off-by: NWei Yongjun <yongjun_wei@trendmicro.com.cn>
Link: https://lkml.kernel.org/r/1406038688-26417-1-git-send-email-weiyj_lk@163.comSigned-off-by: NJason Cooper <jason@lakedaemon.net>

arch/arm/mach-mvebu/pmsu.c

@@ -424,9 +424,9 @@ static int __init armada_xp_pmsu_cpufreq_init(void)
 		}
 
 		clk = clk_get(cpu_dev, 0);
-		if (!clk) {
+		if (IS_ERR(clk)) {
 			pr_err("Cannot get clock for CPU %d\n", cpu);
-			return -ENODEV;
+			return PTR_ERR(clk);
 		}
 
 		/*