documentation: move hpet.txt to timers/ subdirectory

Move hpet.txt to Documentation/timers/ subdirectory.
Add 00-INDEX to Documentation/timers/ subdirectory.

Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Cc: tglx <tglx@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
3 files changed