[MAC80211]: split out some key functions from ieee80211.c

into a new file key.c which doesn't have much code right now but
it makes ieee80211.c easier to read.

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: Jiri Benc <jbenc@suse.cz>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/net/mac80211/Makefile b/net/mac80211/Makefile
index 8482602..d95de3f 100644
--- a/net/mac80211/Makefile
+++ b/net/mac80211/Makefile
@@ -20,4 +20,5 @@
 	ieee80211_cfg.o \
 	rx.o \
 	tx.o \
+	key.o \
 	$(mac80211-objs-y)