mac80211: fix current vs. operating channel in preq/beacon

When sending probe requests, e.g. during software scanning,
these will go out on the *current* channel, so their IEs
need to be built from the current channel. At other times,
e.g. for beacons or probe request templates, the IEs will
be used on the *operating* channel and using the current
channel instead might result in errors.

Add the appropriate parameters to respect the difference.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>