staging: rtl8723au: os_intfs.c: Various cosmetic cleanups

In addition skb->priorty is a u32, so make rtw_classify8021d return a
u32 to match.

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