staging: rtl8723au: Remove unused pointer in rtw_wdev_free()

Pointer 'pwdev_priv' in function rtw_wdev_free() is unused - thus remove it.

Signed-off-by: Christian Engelmayer <cengelma@gmx.at>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>