staging: wfx: retrieve the PS status from the vif

The Power Save status is stored for each virtual interface and for the
whole device. The WF200 is able to handle power saving per interface, so
use the value stored in vif.

Signed-off-by: Jérôme Pouiller <jerome.pouiller@silabs.com>
Link: https://lore.kernel.org/r/20200526171821.934581-6-Jerome.Pouiller@silabs.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>