watchdog: remove dead iop watchdog timer driver

Commit 59d3ae9a ("ARM: remove Intel iop33x and iop13xx support")
removes the config ARCH_IOP13XX in ./arch/arm/Kconfig.

Hence, since then, the corresponding iop watchdog timer driver is dead
code. Remove this dead driver.

Signed-off-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>