watchdog: softdog: remove replaceable ping operation

In watchdog_ping(), 'start' is called automatically when 'ping' function call
is not configured.
Softdog driver has same handling in both cases - start and ping, so 'ping' OPS
can be removed.

Signed-off-by: Milo(Woogyom) Kim <[e-mail]>
Signed-off-by: Wim Van Sebroeck <[e-mail]>

drivers/watchdog/softdog.c

···
 	.owner = THIS_MODULE,
 	.start = softdog_ping,
 	.stop = softdog_stop,
-	.ping = softdog_ping,
 	.set_timeout = softdog_set_timeout,
 };