watchdog: remove at32ap700x_wdt

Since AVR32 is gone, this driver is useless.

Signed-off-by: Corentin Labbe <clabbe.montjoie@gmail.com>
Acked-by: Hans-Christian Noren Egtvedt <egtvedt@samfundet.no>
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>