Make spice dummy functions inline to fix calls not checking return values

qemu_spice_set_passwd() and qemu_spice_set_pw_expire() dummy functions
needs to be inline, in order to handle the case where they are called
without checking the return value.

Signed-off-by: Jes Sorensen <Jes.Sorensen@redhat.com>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>