rt2800usb: slow down TX status polling

Polling TX statuses too frequently has two negative effects. First is
randomly peek CPU usage, causing overall system functioning delays.
Second bad effect is that device is not able to fill TX statuses in
H/W register on some workloads and we get lot of timeouts like below:

ieee80211 phy4: rt2800usb_entry_txstatus_timeout: Warning - TX status timeout for entry 7 in queue 2
ieee80211 phy4: rt2800usb_entry_txstatus_timeout: Warning - TX status timeout for entry 7 in queue 2
ieee80211 phy4: rt2800usb_txdone: Warning - Got TX status for an empty queue 2, dropping

This not only cause flood of messages in dmesg, but also bad throughput,
since rate scaling algorithm can not work optimally.

In the future, we should probably make polling interval be adjusted
automatically, but for now just increase values, this make mentioned
problems gone.

Resolve:
https://bugzilla.kernel.org/show_bug.cgi?id=62781



Cc: stable@vger.kernel.org
Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>