openvswitch: Fix egress tunnel info.

Hello Pravin B Shelar,

This is a semi-automatic email about new static checker warnings.

The patch fc4099f17240: "openvswitch: Fix egress tunnel info." from Oct 22, 2015, leads to the following Smatch complaint:

include/net/dst_metadata.h:69 tun_dst_unclone()
warn: variable dereferenced before check 'md_dst' (see line 66)

include/net/dst_metadata.h

    65		struct metadata_dst *md_dst = skb_metadata_dst(skb);
    66		int md_size = md_dst->u.tun_info.options_len;
                              ^^^^^^^^

New dereference.

    67		struct metadata_dst *new_md;
    68	
    69		if (!md_dst)
                    ^^^^^^^

New NULL check.

    70			return ERR_PTR(-EINVAL);
    71	

regards,
dan carpenter