ACPI / PNP: add soc_button_array device ID to PNP IDs list

The soc_button_array PNP driver was introduced in 3.15.
But in commit eec15edbb0e1 (ACPI / PNP: use device ID list for
PNPACPI device enumeration), when reworking the PNPACPI device
enumeration, we missed the soc_button_array device ID.

This results in a regression in 3.16-rc1 that soc_button_array
pnp device fails to be enumerated.

Fix the problem by adding soc_button_array device ID into the
acpi_pnp scan handler's ID list.

Fixes: eec15edbb0e1 (ACPI / PNP: use device ID list for PNPACPI device enumeration)
Signed-off-by: Zhang Rui <rui.zhang@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Merge branch 'acpi-scan' into bleeding-edge

* acpi-scan:
  ACPI / PNP: add soc_button_array device ID to PNP IDs list