watchdog: softdog: remove obsolete comments

The history is obsolete, especially since we switched to watchdog
framework. The section markers also don't make sense anymore given
the small size of the driver.

Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>