kernel: backport an export required by newer compat-wireless versions

Signed-off-by: Felix Fietkau <nbd@openwrt.org>

SVN-Revision: 44653

target/linux/generic/patches-3.18/030-nl80211-Allow-set-network-namespace-by-fd.patch

@@ -0,0 +1,21 @@
+From: Vadim Kochan <vadim4j@gmail.com>
+Date: Mon, 12 Jan 2015 16:34:05 +0200
+Subject: [PATCH] nl80211: Allow set network namespace by fd
+
+Added new NL80211_ATTR_NETNS_FD which allows to
+set namespace via nl80211 by fd.
+
+Signed-off-by: Vadim Kochan <vadim4j@gmail.com>
+Signed-off-by: Johannes Berg <johannes.berg@intel.com>
+---
+
+--- a/net/core/net_namespace.c
++++ b/net/core/net_namespace.c
+@@ -361,6 +361,7 @@ struct net *get_net_ns_by_fd(int fd)
+ 	return ERR_PTR(-EINVAL);
+ }
+ #endif
++EXPORT_SYMBOL_GPL(get_net_ns_by_fd);
+ 
+ struct net *get_net_ns_by_pid(pid_t pid)
+ {