During my works on the transport layer I removed code that updated
a local variable (is_agg) that is needed to keep the pending_frames
count up to date. Fix this.

Also, there should be no way to have a packet with TX_CTL_AMPDU set
while the internal aggregation state machine is not in AGG_ON state.
Add a WARN_ON to ensure that.
Signed-off-by: NEmmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: NWey-Yi Guy <wey-yi.w.guy@intel.com>
Signed-off-by: NJohn W. Linville <linville@tuxdriver.com>