watchdog: Drop references to H8300 architecture

Architecture is gone.

Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: Wim Van Sebroeck <wim@iguana.be>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>