libpayload-x86: Add PS2 mouse driver

Make use of i8042 driver to add PS2 mouse driver support.

Tested on Lenovot T500.
The touchpad can be used to drive the mouse cursor.

Change-Id: I4be9c74467596b94d64dfa510824d8722108fe9c
Signed-off-by: Patrick Rudolph <siro@das-labor.org>
Reviewed-on: https://review.coreboot.org/18597
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Patrick Georgi <pgeorgi@google.com>
Reviewed-by: Philipp Deppenwiese <zaolin.daisuki@gmail.com>

payloads/libpayload/drivers/mouse_cursor.c

@@ -60,7 +60,9 @@ void mouse_cursor_add_input_driver(struct mouse_cursor_input_driver *const in)
 /** Init enabled mouse cursor drivers */
 void mouse_cursor_init(void)
 {
-/* FIXME */
+#if IS_ENABLED(CONFIG_LP_PC_MOUSE)
+	i8042_mouse_init();
+#endif
 }
 
 static u32 mouse_buttons;