iwl4965: report A-MPDU status

This patch is based on "iwlwifi: report A-MPDU status".
(12bf6f45)

Since the firmware will give us an A-MPDU bit and
only a single PHY information packet for all the
subframes in an A-MPDU, we can easily report the
minimal A-MPDU information for radiotap.

Cc: Stanislaw Gruszka <sgruszka@redhat.com>
Signed-off-by: Christian Lamparter <chunkeey@googlemail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>