documentation: move hpet.txt to timers/ subdirectory

Move hpet.txt to Documentation/timers/ subdirectory.
Add 00-INDEX to Documentation/timers/ subdirectory.
Signed-off-by: NRandy Dunlap <randy.dunlap@oracle.com>
Cc: tglx <tglx@linutronix.de>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>

Documentation/00-INDEX

@@ -161,8 +161,6 @@ hayes-esp.txt
 	- info on using the Hayes ESP serial driver.
 highuid.txt
 	- notes on the change from 16 bit to 32 bit user/group IDs.
-hpet.txt
-	- High Precision Event Timer Driver for Linux.
 timers/
 	- info on the timer related topics
 hw_random.txt

Documentation/timers/00-INDEX

+00-INDEX
+	- this file
+highres.txt
+	- High resolution timers and dynamic ticks design notes
+hpet.txt
+	- High Precision Event Timer Driver for Linux
+hrtimers.txt
+	- subsystem for high-resolution kernel timers
+timer_stats.txt
+	- timer usage statistics