rt2x00: use different txstatus timeouts when flushing

Use different tx status timeouts for normal operation and when flushing.
This increase timeout to 2s for normal operation as when there are bad
radio conditions and frames are reposted many times device can not provide
the status for quite long. With new timeout we can still get valid status
on such bad conditions.

Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>