The ACPI_AC_CLASS symbol is defined in several places in the same way
which is rather unfortunate.
Instead, define it in one common header file (acpi_bus.h) so that it is
accessible to all of its users.
No intentional functional impact.
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Link: https://patch.msgid.link/6163384.MhkbZ0Pkbq@rafael.j.wysocki