cpuidle: Avoid assignment in if () argument

Clean up cpuidle_enable_device() to avoid doing an assignment
in an expression evaluated as an argument of if (), which also
makes the code in question more readable.

Signed-off-by: Gaurav Jindal <gauravjindal1104@gmail.com>
[ rjw: Subject & changelog ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/cpuidle/cpuidle.c

@@ -403,9 +403,11 @@ int cpuidle_enable_device(struct cpuidle_device *dev)
 	if (ret)
 		return ret;
 
-	if (cpuidle_curr_governor->enable &&
-	    (ret = cpuidle_curr_governor->enable(drv, dev)))
-		goto fail_sysfs;
+	if (cpuidle_curr_governor->enable) {
+		ret = cpuidle_curr_governor->enable(drv, dev);
+		if (ret)
+			goto fail_sysfs;
+	}
 
 	smp_wmb();