iwlwifi: acpi: add common code to read from ACPI

There are many places where the same process of invoking a method from
ACPI is used, causing a lot of duplicate code.  To improve this,
introduce a new function to get an ACPI object by invoking an ACPI
method that can be reused.

Additionally, since this function needs to be called when we only have
the trans, the opmode or the device, introduce a new debug macro that
gets the device as a parameter so it can be used in the new function.

Signed-off-by: Luca Coelho <luciano.coelho@intel.com>