iwl4965: disable 8K A-MSDU by default

iwl4965: disable 8K A-MSDU by default

iwlegacy version of this iwlwifi patch:

commit 56f526a0730558f168f744aad96519b40005e89a
Author: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Date:   Wed Feb 20 11:33:00 2013 +0200

    iwlwifi: disable 8K A-MSDU by default

    Supporting 8K A-MSDU means that we need to allocate order 1
    pages for every Rx packet. Even when there is no traffic.
    This adds stress on the memory manager. The handling of
    compound pages is also less trivial for the memory manager
    and not using them will make the allocation code run faster
    although I didn't really measure.
    Eric also pointed out that having huge buffers with little
    data in them is not very nice towards the TCP stack since
    the truesize of the skb is huge. This doesn't allow TCP
    to have a big Rx window.
    See https://patchwork.kernel.org/patch/2167711/ for details.

    Note that very few vendors will actually send A-MSDU.
    Disable this feature by default.

    Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
    Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>