mfd: dln2: Allow to be enumerated via ACPI

On some platforms user may want to enumerate DLN2 device, its children,
to be enumerated via ACPI. In order to achieve this, let's distinguish
children by _ADR value.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>