linux-wandboard

iwlagn: don't stop rts/cts until last aggregation queue close

Once enable rts/cts for aggregation queue, do not disable until the
last aggregation queue closed.

Signed-off-by: Wey-Yi Guy <wey-yi.w.guy@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>