ACPI: thinkpad-acpi: change thinkpad-acpi input default and kconfig help

The current kconfig help text was misleading users.  Also, the default for
an input-layer-optimized support caused way too many problems without
up-to-date userspace in place.

So, rework the help text, and change the default to N.  Note that
distributions are supposed to enable this option as soon as they update HAL
to a version that handles the thinkpad-acpi new input layer interface.

Signed-off-by: Henrique de Moraes Holschuh <hmh@hmh.eng.br>
Cc: Michael S. Tsirkin <mst@dev.mellanox.co.il>
Cc: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Len Brown <len.brown@intel.com>