mfd: cros_ec_spi: Set wakeup capability

Set the device as wakeup capable and register the wakeup source.

Note: Though it makes more sense to have the SPI framework do this,
(either via device tree or by board_info)
this change is as per an existing mail chain:
https://lkml.org/lkml/2009/8/27/291

Signed-off-by: Prathyush K <prathyush.k@samsung.com>
Signed-off-by: Doug Anderson <dianders@chromium.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>

drivers/mfd/cros_ec_spi.c

@@ -381,6 +381,8 @@ static int cros_ec_spi_probe(struct spi_device *spi)
 		return err;
 	}
 
+	device_init_wakeup(&spi->dev, true);
+
 	return 0;
 }