ext4: initialize ret to suppress smatch warning

Signed-off-by: Theodore Ts'o <tytso@mit.edu>

fs/ext4/extents.c

@@ -4382,7 +4382,7 @@ static int ext4_alloc_file_blocks(struct file *file, ext4_lblk_t offset,
 {
 	struct inode *inode = file_inode(file);
 	handle_t *handle;
-	int ret, ret2 = 0, ret3 = 0;
+	int ret = 0, ret2 = 0, ret3 = 0;
 	int retries = 0;
 	int depth = 0;
 	struct ext4_map_blocks map;