staging: rtl8723au: Move FillH2CCmd() prototype to rtl8723a_cmd.h where it really belongs

As an added bonus, remove the now obsolete rtw_ioctl_set.h

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