ACPI: configfs: Make get_header() to return error pointer

Instead of duplicating error codes here and there,
make get_header() to return error pointer.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
1 file changed