spice_channel_read_wire: move variables to internal scope
spice_channel_read_wire: move variables to internal scope

And avoid single line if plus comment

Signed-off-by: Victor Toso <39b7599ff73bbf5db531748ba5250f21fa7120ff@redhat.com>
Acked-by: Christophe Fergeau <05b95054a663c388a4e33d95828cb30f0370f8ef@redhat.com>

flexVDI/spice-gtk,fgouget/spice-gtk,flexVDI/spice-gtk,fgouget/spice-gtk,fgouget/spice-gtk