Revert "platform/x86: ideapad-laptop: Switch touchpad attribute to be RO"

The touchpad can be enabled/disabled via this attribute on a Lenovo
Yoga 520-14IKB. Allow writing as it provides legitimate functionality.

This reverts commit 7f363145.

Signed-off-by: Barnabás Pőcze <pobrn@protonmail.com>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Link: https://lore.kernel.org/r/20210203215403.290792-24-pobrn@protonmail.com


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