controller/test.c: mingw: fix compiler bad param warning for ReadFile
controller/test.c: mingw: fix compiler bad param warning for ReadFile

It seems that ssize_t is int, while DWORD is long

Compiler warning (some whitespaces where added for readability):
  ../../../gtk/controller/test.c: In function 'read_from_pipe':
  ../../../gtk/controller/test.c:108:5: warning: passing argument 4 \
       of 'ReadFile' from incompatible pointer type [enabled by default]
  In file included from /usr/i686-w64-mingw32/sys-root/mingw/include/windows.h:70:0,
                   from ../../../gtk/controller/test.c:27:
  /usr/i686-w64-mingw32/sys-root/mingw/include/winbase.h:1426:29: note: expected \
       'LPDWORD' but argument is of type 'ssize_t *'

Fantu/spice-gtk,Fantu/spice-gtk,mathslinux/spice-gtk,mathslinux/spice-gtk,guodong/spice-gtk,elmarco/spice-gtk,elmarco/spice-gtk,guodong/spice-gtk,dezelin/spice-gtk,elmarco/spice-gtk,fgouget/spice-gtk,flexVDI/spice-gtk,elmarco/spice-gtk,freedesktop-unofficial-mirror/spice__spice-gtk,mathslinux/spice-gtk,SPICE/spice-gtk,flexVDI/spice-gtk,freedesktop-unofficial-mirror/spice__spice-gtk,guodong/spice-gtk,SPICE/spice-gtk,guodong/spice-gtk,fgouget/spice-gtk,Fantu/spice-gtk,dezelin/spice-gtk,freedesktop-unofficial-mirror/spice__spice-gtk,SPICE/spice-gtk,mathslinux/spice-gtk,Fantu/spice-gtk,dezelin/spice-gtk,SPICE/spice-gtk,freedesktop-unofficial-mirror/spice__spice-gtk,dezelin/spice-gtk,fgouget/spice-gtk