platform/x86: intel-vbtn: Create 2 separate input-devs for buttons and switches

Create 2 separate input-devs for buttons and switches, this is a
preparation for dynamically registering the switches-input device
for devices which are not on the switches allow-list, but do make
Notify() calls with an event value from the switches sparse-keymap.

This also brings the intel-vbtn driver inline with the intel-hid
driver which is doing the same thing.

Cc: Elia Devito <eliadevito@gmail.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Link: https://lore.kernel.org/r/20210115161850.117614-2-hdegoede@redhat.com