efi/apple-properties: use PROPERTY_ENTRY_U8_ARRAY_LEN

Let's switch to using PROPERTY_ENTRY_U8_ARRAY_LEN() to initialize
property entries. Also, when dumping data, rely on local variables
instead of poking into the property entry structure directly.

Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>