ACPI / EC: access user space with get_user()/put_user()

User space pointer may not be dereferenced. Use get_user()/put_user()
instead and check their return codes.

Signed-off-by: Vasiliy Kulikov <segooon@gmail.com>
Signed-off-by: Thomas Renninger <trenn@suse.de>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>