iwlwifi: fix max_ht_ampdu_exponent for older devices

iwlwifi: fix max_ht_ampdu_exponent for older devices

commit 540623caa6c769d9d19e6044949f5fa2fe1a33a6 upstream.

The commit below didn't update the max_ht_ampdu_exponent
for the devices listed in iwl-[1-6]000.c which, in result,
became 0 instead of 8K. This reduced the size of the Rx
AMPDU from 64K to 8K which had an impact in the Rx
throughput. One user reported that because of this, his
downstream throughput droppped by a half.

Fixes: c064ddf318aa ("iwlwifi: change max HT and VHT A-MPDU exponent")
Reported-and-tested-by: Valentin Manea <linux-wireless@mrs.ro>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>