platform/x86: ideapad-laptop: send notification about touchpad state change to sysfs

platform/x86: ideapad-laptop: send notification about touchpad state change to sysfs

Consumers can determine if the value of an attribute changed much more
easily if changes are broadcast using sysfs_notify(), so utilize it.

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/20210203215403.290792-26-pobrn@protonmail.com
Signed-off-by: Hans de Goede <hdegoede@redhat.com>