Revert "Input: elantech - enable SMBus on new (2018+) systems"

This reverts commit 883a2a80f79ca5c0c105605fafabd1f3df99b34c.

Apparently use dmi_get_bios_year() as manufacturing date isn't accurate
and this breaks older laptops with new BIOS update.

So let's revert this patch.

There are still new HP laptops still need to use SMBus to support all
features, but it'll be enabled via a whitelist.

Signed-off-by: Kai-Heng Feng <kai.heng.feng@canonical.com>
Acked-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20191001070845.9720-1-kai.heng.feng@canonical.com
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>