staging: most: Delete an unnecessary check before the function call "module_put"

The module_put() function tests whether its argument is NULL and then
returns immediately. Thus the test around the call is not needed.

This issue was detected by using the Coccinelle software.
Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/most/mostcore/core.c

@@ -1587,7 +1587,6 @@ int most_start_channel(struct most_interface *iface, int id,
 	return 0;
 
 error:
-	if (iface->mod)
 	module_put(iface->mod);
 	modref--;
 	mutex_unlock(&c->start_mutex);