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/[e-mail]
Signed-off-by: Chengguang Xu <[e-mail]>
Signed-off-by: Jan Kara <[e-mail]>

fs/ext2/super.c

···
 				ext2_count_dirs(sb), GFP_KERNEL);
 	}
 	if (err) {
+		ret = err;
 		ext2_msg(sb, KERN_ERR, "error: insufficient memory");
 		goto failed_mount3;
 	}