usb_api.h: Stub usb_wake if CONFIG_USB_REMOTE_WAKEUP is not defined

Removes clutter in callers, so that they do not have to wrap
usb_wake calls around ifdefs.

BRANCH=none
BUG=none
TEST=make buildall -j

Change-Id: I8641cb7aff702920aaa119e644dc812d5c3e774b
Signed-off-by: Nicolas Boichat <drinkcat@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/612220
Reviewed-by: Vincent Palatin <vpalatin@chromium.org>

chip/stm32/usb_hid_keyboard.c

@@ -211,10 +211,8 @@ static void write_keyboard_report(void)
 				EP_TX_VALID, 0);
 	}
 
-#ifdef CONFIG_USB_REMOTE_WAKEUP
 	/* Wake up host, if required. */
 	usb_wake();
-#endif
 }
 
 static void hid_keyboard_tx(void)

chip/stm32/usb_hid_touchpad.c

@@ -179,10 +179,8 @@ void set_touchpad_report(struct usb_hid_touchpad_report *report)
 	/* enable TX */
 	STM32_TOGGLE_EP(USB_EP_HID_TOUCHPAD, EP_TX_MASK, EP_TX_VALID, 0);
 
-#ifdef CONFIG_USB_REMOTE_WAKEUP
 	/* Wake up host, if required. */
 	usb_wake();
-#endif
 }
 
 static void hid_touchpad_tx(void)

include/usb_api.h

@@ -49,12 +49,16 @@ void usb_release(void);
 int usb_is_suspended(void);
 
 /*
- * Tell the host to wake up. Requires CONFIG_USB_REMOTE_WAKEUP to be defined,
- * and a chip that implements the function.
+ * Tell the host to wake up. Does nothing if CONFIG_USB_REMOTE_WAKEUP is not
+ * defined.
  *
  * Returns immediately, suspend status can be checked using usb_is_suspended.
  */
+#ifdef CONFIG_USB_REMOTE_WAKEUP
 void usb_wake(void);
+#else
+static inline void usb_wake(void) {}
+#endif
 
 /* Board-specific USB wake, for side-band wake, called by usb_wake above. */
 void board_usb_wake(void);