staging: wfx: drop useless argument from wfx_set_pm()

Argument to wfx_set_pm() is always wvif->powersave_mode. So, we can
simplify it.

Signed-off-by: Jérôme Pouiller <jerome.pouiller@silabs.com>
Link: https://lore.kernel.org/r/20191217161318.31402-33-Jerome.Pouiller@silabs.com


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