platform/x86: thinkpad_acpi: fix documentation for adaptive keyboard

The different values were offset by 1. 0 is for "home mode", 1 for
"web-browser mode", etc. Moreover, the URL to the laptop's user guide
did not work anymore.

Signed-off-by: Vincent Bernat <vincent@bernat.ch>
Link: https://lore.kernel.org/r/20211109195209.176905-1-vincent@bernat.ch


Signed-off-by: Hans de Goede <hdegoede@redhat.com>