[MAC80211]: introduce util.c

Introduce a new file util.c and move a whole bunch of functions into it.

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 d95de3f..122b23e 100644
--- a/net/mac80211/Makefile
+++ b/net/mac80211/Makefile
@@ -21,4 +21,5 @@
 	rx.o \
 	tx.o \
 	key.o \
+	util.o \
 	$(mac80211-objs-y)