wilc1000: Improve WILC TX performance when power_save is off

The wakeup and sleep commands need to be sent to the WILC chip only
when it is in power save mode (PSM, as controlled by "iw dev wlan0 set
power_save on/off").  The commands are relatively costly, so it pays
to skip them when possible.

iperf3 without this patch (no significant different with PSM on/off):
  TX   0.00-120.01 sec   140 MBytes  9.82 Mbits/sec
  RX   0.00-120.69 sec   283 MBytes  19.6 Mbits/sec

with this patch applied:

PSM off (TX is 46% improved, RX slightly improved; may not be significant):
  TX   0.00-120.00 sec   206 MBytes  14.4 Mbits/sec
  RX   0.00-120.48 sec   322 MBytes  22.4 Mbits/sec

PSM on (no significant change):
  TX   0.00-120.00 sec   140 MBytes  9.78 Mbits/sec
  RX   0.00-120.08 sec   257 MBytes  18.0 Mbits/sec

Signed-off-by: David Mosberger-Tang <davidm@egauge.net>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/20211210203016.3680425-2-davidm@egauge.net