Fix offchannel TX not to retransmit pending frame on callback

Fix offchannel TX not to retransmit pending frame on callback

If the offchannel TX frame command was offloaded to the driver in
offchannel_send_action(), we must not send another copy of the frame if
a remain-on-channel event happens to be delivered between this TX
command and the matching TX status event. It was possible for the
duplicated frame to cause problems, e.g., with P2P invitation exchange
if the same Invitation Request frame got sent twice and only the first
one getting accepted by the peer.

Signed-off-by: Jouni Malinen <jouni@qca.qualcomm.com>