CHROMIUMOS: mac80211: Set beacon loss detection parameters to be more lenient

CHROMIUMOS: mac80211: Set beacon loss detection parameters to be more lenient

This is a workaround to reduce the impact of bug 4886 while we
attempt to get a proper fix in.  This will allow us to cling to
the AP a bit longer while the receiver is stuck.

Signed-off-by: Paul Stewart <pstew@chromium.org>
BUG=chrome-os-partner:4886
TEST=TEST=Manual: Bench-top re-enactment of congested environment +
in-field testing with client machines

Change-Id: I92d5f405287787ee75a78644de36c33b53685a10
Reviewed-on: https://gerrit.chromium.org/gerrit/15862
Reviewed-by: Sam Leffler <sleffler@chromium.org>
Tested-by: Paul Stewart <pstew@chromium.org>
Commit-Ready: Paul Stewart <pstew@chromium.org>