wifi: libertas: Remove unused auto deep sleep code

With the recent removal of the uncalled
  lbs_(enter|exit)_auto_deep_sleep()
functions, it's no longer possible to set
  priv->is_auto_deep_sleep_enabled
so we can remove all tests of it and the variable itself.

With that gone, priv->wakeup_dev_required also doesn't
get set, so we can remove any testing of it.

Now the timer itself, and the function it calls goes.
The timer used the apparently unset auto_deep_sleep_timeout
member, which can also go.

Signed-off-by: Dr. David Alan Gilbert <linux@treblig.org>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://patch.msgid.link/20250121013300.433538-4-linux@treblig.org