watchdog: documentation: remove index-file

The 00-index file in the watchdog directory is, like many others,
outdated (conversion-howto is missing) and doesn't contain worthwhile
additional information. As it seems to be a maintenance burden without
much gain, simply remove it.
Signed-off-by: NWolfram Sang <w.sang@pengutronix.de>
Signed-off-by: NWim Van Sebroeck <wim@iguana.be>

Documentation/watchdog/00-INDEX

-00-INDEX
-	- this file.
-convert_drivers_to_kernel_api.txt
-	- how-to for converting old watchdog drivers to the new kernel API.
-hpwdt.txt
-	- information on the HP iLO2 NMI watchdog
-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.
-watchdog-kernel-api.txt
-	- description of the Linux WatchDog Timer Driver Core kernel API.
-watchdog-parameters.txt
-	- information on driver parameters (for drivers other than
-	  the ones that have driver-specific files here)
-wdt.txt
-	- description of the Watchdog Timer Interfaces for Linux.