greybus: arche-apb-ctrl: Set wake_detect gpio to low initially

This patch enables handshaking of AP and SVC using wake_detect
gpio (WD_8A and WD_8B).
Note that WAKE_DETECT polarity is active-high, so in order to
enable handshaking between AP <=> SVC, we need to set wake_detect
gpio to low initially, so that driver can send WAKE_DET signal
(active-high) to SVC and then SVC can send back WAKE_MOD signal
(active-low).
And on reception of WAKE_MOD signal, driver would bring respective
APB out of reset.

  WD_8A => APB1
  WD_8B => APB2
Signed-off-by: Vaibhav Hiremath <vaibhav.hiremath@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>

drivers/staging/greybus/arche-apb-ctrl.c

@@ -195,7 +195,8 @@ static int apb_ctrl_init_seq(struct platform_device *pdev,
 	gpio_set_value(apb->boot_ret_gpio, 0);
 	udelay(50);
 
-	ret = devm_gpio_request(dev, apb->wake_detect_gpio, "wake detect");
+	ret = devm_gpio_request_one(dev, apb->wake_detect_gpio,
+			GPIOF_INIT_LOW, "wake detect");
 	if (ret)
 		dev_err(dev, "Failed requesting wake_detect gpio %d\n",
 				apb->wake_detect_gpio);