usb: gadget: storage_common: use kstrto*() [bug fix]

This commit fixes an embarrassing bug in the "storage_common:
use kstrto*()" patch which caused fsg_store_ro() to return
zero instead of the length of the consumed buffer.
Signed-off-by: Michal Nazarewicz <mina86@mina86.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/usb/gadget/storage_common.c

@@ -708,7 +708,7 @@ static ssize_t fsg_show_file(struct device *dev, struct device_attribute *attr,
 static ssize_t fsg_store_ro(struct device *dev, struct device_attribute *attr,
 			    const char *buf, size_t count)
 {
-	ssize_t		rc = count;
+	ssize_t		rc;
 	struct fsg_lun	*curlun = fsg_lun_from_dev(dev);
 	struct rw_semaphore	*filesem = dev_get_drvdata(dev);
 	unsigned	ro;
@@ -729,6 +729,7 @@ static ssize_t fsg_store_ro(struct device *dev, struct device_attribute *attr,
 		curlun->ro = ro;
 		curlun->initially_ro = ro;
 		LDBG(curlun, "read-only status set to %d\n", curlun->ro);
+		rc = count;
 	}
 	up_read(filesem);
 	return rc;