Some APs (e.g. TP-LINK TL-WA801N) are disabling aggregation (downlink
to station) when U-APSD is enabled, resulting in low throughput.
Add a module parameter to allow disabling U-APSD support in the driver.

Also re-enable U-APSD for -9 firmware since the firmare issues were
fixed in this release.

There are devices that won't support U-APSD even with newer
firmware, so bring the TLV flag back to detect those.
Signed-off-by: Matt Chen <matt.chen@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>