drivers/pc80: Add PS/2 mouse presence detect

On certain Winbond SuperIO devices, when a PS/2 mouse is not
present on the auxiliary channel both channels will cease to
function if the auxiliary channel is probed while the primary
channel is active.  Therefore, knowledge of mouse presence
must be gathered by coreboot during early boot, and used to
enable or disable the auxiliary PS/2 port before control is
passed to the operating system.

Add auxiliary channel PS/2 device presence detect, and update
the Winbond W83667HG-A driver to flag the auxiliary channel as
disabled if no device was detected.

Change-Id: I76274493dacc9016ac6d0dff8548d1dc931c6266
Signed-off-by: Timothy Pearson <tpearson@raptorengineeringinc.com>
Reviewed-on: https://review.coreboot.org/13165
Tested-by: build bot (Jenkins)
Tested-by: Raptor Engineering Automated Test Stand <noreply@raptorengineeringinc.com>
Reviewed-by: Martin Roth <martinroth@google.com>

src/superio/ite/it8718f/superio.c

@@ -34,7 +34,7 @@ static void init(struct device *dev)
 	case IT8718F_EC: /* TODO. */
 		break;
 	case IT8718F_KBCK:
-		pc_keyboard_init();
+		pc_keyboard_init(NO_AUX_DEVICE);
 		break;
 	case IT8718F_KBCM: /* TODO. */
 		break;