Try to improve sys/i386 maintainability by removing bunch of #ifdefs for XBOX.
It is for console presented at 2001 and featuring Pentium III processor. Even if any of them are still alive and run FreeBSD, we do not have any sign of life from their users. While removing another dozens of #ifdefs from the i386 sources reduces the aversion from looking at the code and improves the platform vitality. This accompaines earlier removal of the XEN PVM pollution.