watchdog: JZ4740: Drop module remove function

When the watchdog was configured for nowayout, and after the
userspace watchdog daemon closed the dev node without sending the
magic character, unloading this module stopped the watchdog
hardware, which was clearly a problem.

Besides, unloading the module is not possible when the userspace
watchdog daemon is running, so it's safe to assume that we don't
need to stop the watchdog hardware in the jz4740_wdt_remove()
function.

For this reason, the jz4740_wdt_remove() function can then be
dropped alltogether.

Signed-off-by: Paul Cercueil <paul@crapouillou.net>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Cc: Wim Van Sebroeck <wim@linux-watchdog.org>
Cc: Mathieu Malaterre <malat@debian.org>
Cc: linux-watchdog@vger.kernel.org
Cc: linux-mips@linux-mips.org
Signed-off-by: James Hogan <jhogan@kernel.org>