mac80211: make ieee80211_new_mesh_header return unsigned

The function returns always non-negative values.

The problem has been detected using proposed semantic patch
scripts/coccinelle/tests/assign_signed_to_unsigned.cocci [1].

[1]: http://permalink.gmane.org/gmane.linux.kernel/2046107

Signed-off-by: Andrzej Hajda <a.hajda@samsung.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/mac80211/mesh.c

@@ -606,9 +606,9 @@ int ieee80211_fill_mesh_addresses(struct ieee80211_hdr *hdr, __le16 *fc,
  *
  * Return the header length.
  */
-int ieee80211_new_mesh_header(struct ieee80211_sub_if_data *sdata,
-			      struct ieee80211s_hdr *meshhdr,
-			      const char *addr4or5, const char *addr6)
+unsigned int ieee80211_new_mesh_header(struct ieee80211_sub_if_data *sdata,
+				       struct ieee80211s_hdr *meshhdr,
+				       const char *addr4or5, const char *addr6)
 {
 	if (WARN_ON(!addr4or5 && addr6))
 		return 0;

net/mac80211/mesh.h

@@ -207,9 +207,9 @@ struct mesh_rmc {
 /* Various */
 int ieee80211_fill_mesh_addresses(struct ieee80211_hdr *hdr, __le16 *fc,
 				  const u8 *da, const u8 *sa);
-int ieee80211_new_mesh_header(struct ieee80211_sub_if_data *sdata,
-			      struct ieee80211s_hdr *meshhdr,
-			      const char *addr4or5, const char *addr6);
+unsigned int ieee80211_new_mesh_header(struct ieee80211_sub_if_data *sdata,
+				       struct ieee80211s_hdr *meshhdr,
+				       const char *addr4or5, const char *addr6);
 int mesh_rmc_check(struct ieee80211_sub_if_data *sdata,
 		   const u8 *addr, struct ieee80211s_hdr *mesh_hdr);
 bool mesh_matches_local(struct ieee80211_sub_if_data *sdata,