syntax-check: fix cast_of_argument_to_free
syntax-check: fix cast_of_argument_to_free

In this case, make syntax-check is wrong, and we actually do
need the cast.
A cast is needed when types are   uint64_t <--> pointer

Using a local "ptr" variable makes both gcc and syntax-check happy.

SPICE/spice,elmarco/spice,Fantu/spice,alon/spice-server,freedesktop-unofficial-mirror/spice__spice,Fantu/spice,fgouget/spice,fgouget/spice,fgouget/spice,freedesktop-unofficial-mirror/spice__spice,SPICE/spice,elmarco/spice,fgouget/spice,elmarco/spice,elmarco/spice,SPICE/spice,alon/spice-server,Fantu/spice,ya-mouse/spice,ya-mouse/spice,Fantu/spice,freedesktop-unofficial-mirror/spice__spice,elmarco/spice,ya-mouse/spice,alon/spice-server,alon/spice-server,alon/spice-server,freedesktop-unofficial-mirror/spice__spice,freedesktop-unofficial-mirror/spice__spice