hwmon: (ams) Fix locking issues

Use a separate mutex to serialize input device creation/removal,
otheriwse we deadlock if we try to remove input device while it is
being polled. Also do not take ams_info.lock when it is not needed.

Signed-off-by: Dmitry Torokhov <dtor@mail.ru>
Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: Jean Delvare <khali@linux-fr.org>
diff --git a/drivers/hwmon/ams/ams-pmu.c b/drivers/hwmon/ams/ams-pmu.c
index 9463e97..fb18b3d 100644
--- a/drivers/hwmon/ams/ams-pmu.c
+++ b/drivers/hwmon/ams/ams-pmu.c
@@ -149,8 +149,6 @@
 	const u32 *prop;
 	int result;
 
-	mutex_lock(&ams_info.lock);
-
 	/* Set implementation stuff */
 	ams_info.of_node = np;
 	ams_info.exit = ams_pmu_exit;
@@ -161,10 +159,9 @@
 
 	/* Get PMU command, should be 0x4e, but we can never know */
 	prop = of_get_property(ams_info.of_node, "reg", NULL);
-	if (!prop) {
-		result = -ENODEV;
-		goto exit;
-	}
+	if (!prop)
+		return -ENODEV;
+
 	ams_pmu_cmd = ((*prop) >> 8) & 0xff;
 
 	/* Disable interrupts */
@@ -175,7 +172,7 @@
 
 	result = ams_sensor_attach();
 	if (result < 0)
-		goto exit;
+		return result;
 
 	/* Set default values */
 	ams_pmu_set_register(AMS_FF_LOW_LIMIT, 0x15);
@@ -198,10 +195,5 @@
 
 	printk(KERN_INFO "ams: Found PMU based motion sensor\n");
 
-	result = 0;
-
-exit:
-	mutex_unlock(&ams_info.lock);
-
-	return result;
+	return 0;
 }