HID: Rename some code identifiers from PowerBook specific to Apple generic

Preserve identifiers exposed in build and run time configuration though in
order not to break existing configurations.

This is in preparation for adding support for Apple aluminum USB keyboards.

Signed-off-by: Michel Daenzer <michel@tungstengraphics.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>