HID: google: add dependency on Cros EC for Hammer

Whiskers tablet mode support needs access to Chrome Embedded Controller,
so we need to add dependency on MFD_CROS_EC.
Reported-by: kbuild test robot <lkp@intel.com>
Fixes: eb1aac4c ("HID: google: add support tablet mode switch for Whiskers")
Signed-off-by: Dmitry Torokhov <dtor@chromium.org>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

drivers/hid/Kconfig

@@ -351,7 +351,7 @@ config HOLTEK_FF
 
 config HID_GOOGLE_HAMMER
 	tristate "Google Hammer Keyboard"
-	depends on USB_HID && LEDS_CLASS
+	depends on USB_HID && LEDS_CLASS && MFD_CROS_EC
 	---help---
 	Say Y here if you have a Google Hammer device.