bcmdhd: Enable Ad-Hoc (IBSS) mode

Enable Ad-Hoc (IBSS) mode for bcmdhd. We basically just need to set the
interface flag and avoid some P2P specific settings while scanning.

Also add the "station get" command for IBSS mode.

Change-Id: Ie6f0fa77b55d92a7c22cbda72bad200cbfaede04
Signed-off-by: Bruno Randolf <br1@einfach.org>