SUNRPC/cache: add module_put() on error path in cache_open()

If kmalloc() fails in cache_open(), module cd->owner left locked.
The patch adds module_put(cd->owner) on this path.

Found by Linux Driver Verification project (linuxtesting.org).
Signed-off-by: Alexey Khoroshilov <khoroshilov@ispras.ru>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

net/sunrpc/cache.c

@@ -986,8 +986,10 @@ static int cache_open(struct inode *inode, struct file *filp,
 	nonseekable_open(inode, filp);
 	if (filp->f_mode & FMODE_READ) {
 		rp = kmalloc(sizeof(*rp), GFP_KERNEL);
-		if (!rp)
+		if (!rp) {
+			module_put(cd->owner);
 			return -ENOMEM;
+		}
 		rp->offset = 0;
 		rp->q.reader = 1;
 		atomic_inc(&cd->readers);