Use 0xffu everywhere in new SPICE_MAGIC_CONST macro
Use 0xffu everywhere in new SPICE_MAGIC_CONST macro

This should have been squashed in the commit introducing the macro, but
I forgot to commit this before pushing it.

fgouget/spice-protocol,SPICE/spice-protocol,fgouget/spice-protocol,fgouget/spice-protocol,vdiot/spice-protocol,vdiot/spice-protocol,SPICE/spice-protocol,SPICE/spice-protocol,vdiot/spice-protocol