iwlwifi: mvm: update TX queue before making a copy of the skb

Off-channel action frames (such as ANQP frames) must be sent either on
the AUX queue or on the offchannel queue, otherwise the firmware will
cause a SYSASSERT.

In the current implementation, the queue to be used is correctly set in
the original skb, but this is done after it is copied.  Thus the copy
remains with the original, incorrect queue.

Fix this by setting the queue in the original skb before copying it.

Fixes: commit 5c08b0f5 ("iwlwifi: mvm: don't override the rate with the AMSDU len")
Cc: stable@vger.kernel.org # v4.6+
Signed-off-by: Beni Lev <beni.lev@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>