iwlagn: warn about buggy fw that doesn't set SEQ_RX_FRAME

The way we check if there is host command that should be reclaimed is
way too complicated. We should have a clear indication from the fw.
The fw is expected to set the SEQ_RX_FRAME bit if the frame was
originated by the fw which indicates to the driver that there is no
host command to free.
Somehow, there seem to have been buggy fw out there, hence the very
old comment.

This code checks if we have still buggy fw out there.

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