Eliminated the arch/i386/kernel/timers in 2.6.18, use clocksoures instead.
pit_latch_buggy was referred in timers/timer_tsc.c, and currently removed.
Therefore nobody refer it.
Until 2.6.17, MediaGX's TSC works correctly. after 2.6.18, warned "TSC
appears to be running slowly. Marking it as unstable". So marked unstable
TSC when CS55x0.