mac80211: Do not check for valid hw_queues for P2P_DEVICE

A P2P Device interface does not have a netdev, and is not
expected to be used for transmitting data, so there is no
need to assign hw queues for it.

Signed-off-by: Ilan Peer <ilan.peer@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>