[WATCHDOG] Add a 00-INDEX file to Documentation/watchdog/

Add a 00-INDEX file to Documentation/watchdog/
Signed-off-by: Jesper Juhl <jesper.juhl@gmail.com>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>

Documentation/watchdog/00-INDEX

+00-INDEX
+	- this file.
+pcwd-watchdog.txt
+	- documentation for Berkshire Products PC Watchdog ISA cards.
+src/
+	- directory holding watchdog related example programs.
+watchdog-api.txt
+	- description of the Linux Watchdog driver API.
+wdt.txt
+	- description of the Watchdog Timer Interfaces for Linux.