This patch adds a check to the set_channel flow. When attempting to change
the channel while in IBSS mode, and the new channel does not support IBSS
mode, the flow return with an error value with no consequences on the
mac80211 and driver state.

Signed-off-by: Assaf Krauss <assaf.krauss@intel.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>