mac80211: refactor the parsing of chan switch ie

Refactor the channel switch IE parsing to reduce the number
of function parameters.

Signed-off-by: Chun-Yeow Yeoh <yeohchunyeow@cozybit.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

diff --cc net/mac80211/ibss.c
Simple merge

diff --cc net/mac80211/ieee80211_i.h
Simple merge

diff --cc net/mac80211/mlme.c
Simple merge

diff --cc net/mac80211/spectmgmt.c
Simple merge