Remove warning about unused variable when building on macOS
Remove warning about unused variable when building on macOS

On macOS, neither of the two cases implemented in set_mouse_accel applies.
We get the following eror message:

  CC       spice-widget.lo
spice-widget.c:944:26: error: unused variable 'd' [-Werror,-Wunused-variable]
    SpiceDisplayPrivate *d = display->priv;

Acked-by: Frediano Ziglio <55d48b080b2e443e395cde84d2c83b135a4ff48e@redhat.com>
Signed-off-by: Christophe de Dinechin <e3d13d45b866407e72234c83bf86018df4b2ef13@redhat.com>

flexVDI/spice-gtk,flexVDI/spice-gtk