staging: rtl8723au: Remove two never set variables

struct registry_priv.usbss_enable and
struct pwrctrl_priv.bHWPwrPindetect are never set.

Signed-off-by: Jes Sorensen <Jes.Sorensen@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>