Allow to setup maximum subframes for AMSDU and AMPDU aggregation
via debugfs htt_max_amsdu_ampdu file.

Eg.
echo "2 64" > htt_max_amsdu_ampdu
will setup maximum amsdu subframes equal 2 and
maximum ampdu subframes equal to 64.
Signed-off-by: Janusz Dziedzic <janusz.dziedzic@tieto.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>