Documentation/watchdog/hpwdt: Fix Reference

The IPMI documentation moved to Documentation/driver-api/ipmi.rst.
Update reference to reflect new location.

Signed-off-by: Jerry Hoemann <jerry.hoemann@hpe.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20230210184247.221134-2-jerry.hoemann@hpe.com
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/watchdog/hpwdt.rst

@@ -48,7 +48,7 @@ Last reviewed: 08/20/2018
  NOTE:
        More information about watchdog drivers in general, including the ioctl
        interface to /dev/watchdog can be found in
-       Documentation/watchdog/watchdog-api.rst and Documentation/IPMI.txt.
+       Documentation/watchdog/watchdog-api.rst and Documentation/driver-api/ipmi.rst
 
  Due to limitations in the iLO hardware, the NMI pretimeout if enabled,
  can only be set to 9 seconds.  Attempts to set pretimeout to other