ext2: set proper errno in error case of ext2_fill_super()

Set proper errno in the case of failure of
initializing percpu variables.

Link: https://lore.kernel.org/r/20191129013636.7624-1-cgxu519@mykernel.net
Signed-off-by: Chengguang Xu <cgxu519@mykernel.net>
Signed-off-by: Jan Kara <jack@suse.cz>

fs/ext2/super.c

@@ -1138,6 +1138,7 @@ static int ext2_fill_super(struct super_block *sb, void *data, int silent)
 				ext2_count_dirs(sb), GFP_KERNEL);
 	}
 	if (err) {
+		ret = err;
 		ext2_msg(sb, KERN_ERR, "error: insufficient memory");
 		goto failed_mount3;
 	}