Input: soc_button_array - use NULL for GPIO connection ID

The gpiolib-acpi code is becoming more strict and connection-IDs
may only be used with devices which have a _DSD with matching IDs
in there. Since the soc_button_array ACPI binding is pure index
based pass in NULL as connection-ID to avoid the more strict cheks
resulting in gpiod_count and gpiod_get_index not returning any gpios.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>