On AM62x, the watchdog is pet before the valid window is open. Fix
min_hw_heartbeat and accommodate a 2% + static offset safety margin.
The static offset accounts for max hardware error.

Remove the hack in the driver which shifts the open window boundary,
since it is no longer necessary due to the fix mentioned above.

cc: stable@vger.kernel.org
Fixes: 5527483f ("watchdog: rti-wdt: attach to running watchdog during probe")
Signed-off-by: Judith Mendez <jm@ti.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20240417205700.3947408-1-jm@ti.comSigned-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>