Input: inexio - constify serio_device_id

serio_device_id are not supposed to change at runtime. All functions
working with serio_device_id provided by <linux/serio.h> work with
const serio_device_id. So mark the non-const structs as const.

Signed-off-by: Arvind Yadav <arvind.yadav.cs@gmail.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>