ARM: cpuidle: Fix error return code

We know that 'ret = 0' because it has been tested a few lines above.
So, if 'kzalloc' fails, 0 will be returned instead of an error code.
Return -ENOMEM instead.

Fixes: a0d46a3dfdc3 ("ARM: cpuidle: Register per cpuidle device")
Signed-off-by: Christophe Jaillet <christophe.jaillet@wanadoo.fr>
Acked-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Cc: 4.1+ <stable@vger.kernel.org> # 4.1+
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/cpuidle/cpuidle-arm.c

@@ -135,6 +135,7 @@ static int __init arm_idle_init(void)
 		dev = kzalloc(sizeof(*dev), GFP_KERNEL);
 		if (!dev) {
 			pr_err("Failed to allocate cpuidle device\n");
+			ret = -ENOMEM;
 			goto out_fail;
 		}
 		dev->cpu = cpu;