macintosh/ams-input: switch to using input device polling mode

Now that instances of input_dev support polling mode natively,
we no longer need to create input_polled_dev instance.

Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20191002214854.GA114387@dtor-ws