Fix the following warning (Building: ci20_defconfig mips):

drivers/watchdog/jz4740_wdt.c: In function ‘jz4740_wdt_probe’:
drivers/watchdog/jz4740_wdt.c:165:6: warning: unused variable ‘ret’ [-Wunused-variable]
  int ret;
      ^~~
Fixes: 9ee644c9 ("watchdog: jz4740_wdt: drop warning after registering device")
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20190806073953.GA13685@embeddedorSigned-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>