win32: pair qemu_memalign() with qemu_vfree()

Win32 suffers from a very big memory leak when dealing with SCSI devices.
Each read/write request allocates memory with qemu_memalign (ie
VirtualAlloc) but frees it with qemu_free (ie free).
Pair all qemu_memalign() calls with qemu_vfree() to prevent such leaks.

Signed-off-by: Herve Poussineau <hpoussin@reactos.org>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

qemu-nbd.c

@@ -469,7 +469,7 @@ int main(int argc, char **argv)
             }
         }
     } while (persistent || nb_fds > 1);
-    qemu_free(data);
+    qemu_vfree(data);
 
     close(sharing_fds[0]);
     bdrv_close(bs);