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 <milo.kim@ti.com>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>
diff --git a/drivers/watchdog/softdog.c b/drivers/watchdog/softdog.c
index fe83beb8..b68b1e5 100644
--- a/drivers/watchdog/softdog.c
+++ b/drivers/watchdog/softdog.c
@@ -152,7 +152,6 @@
 	.owner = THIS_MODULE,
 	.start = softdog_ping,
 	.stop = softdog_stop,
-	.ping = softdog_ping,
 	.set_timeout = softdog_set_timeout,
 };