rtlwifi: Initialize power-setting callback for USB devices

rtlwifi: Initialize power-setting callback for USB devices

commit bcfb879432094c267c35a7ff75d953d3a66c193a upstream.

Commit a269913c5 entitled "rtlwifi: Rework rtl_lps_leave() and
rtl_lps_enter() to use work queue" has two bugs for USB drivers.
Firstly, the work queue in question was not initialized. Secondly,
the callback routine used by this queue is contained within the
file used for PCI devices. As a result, it is not available for
architectures without PCI hardware.

Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Reported-by: Richard Genoud <richard.genoud@gmail.com>
Tested-by: Richard Genoud <richard.genoud@gmail.com>
Cc: Richard Genoud <richard.genoud@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>