rtl8723ae: Take the FW LPS mode handling out

This appears to trigger a firmware bug and causes severe
problems with rtl8723ae PCI devices.

When the power save mode is activated for longer periods
of time the firmware stops to receive any packets.

This problem was exposed by commit 873ffe15 ("rtlwifi:
Fix logic error in enter/exit power-save mode").

Previously the power save mode was only active rarely and
only for a short time so that the problem was not noticeable.

Signed-off-by: Bernd Edlinger <bernd.edlinger@hotmail.de>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>