ath6kl: Fix unstable downlink throughput

There is frequent downlink throughput drop to 0 when operating
at the signal level between -42dBm to -53dBm. This has been root
caused to the delay in releasing pending a-mpdu subframes in
reorder buffer. Right now the timeout value is 400ms, there
is also a race condition where timeout handler can be delayed
to run at an extra timeout interval. This patch reduces the
timout interval to reasonable 100ms and makes sure releasing
pending frames are not skipped in the timeout handler by removing
the flag (rxtid->progress) which can delay the timeout logic.

Reported-by: Yu Yanzhi <yanzhiy@qca.qualcomm.com>
Signed-off-by: Vasanthakumar Thiagarajan <vthiagar@qca.qualcomm.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>