devcoredump: avoid -Wempty-body warnings

Cleaning out the last -Wempty-body warnings found some interesting
cases with empty macros, along with harmless warnings like this one:

drivers/base/devcoredump.c: In function 'dev_coredumpm':
drivers/base/devcoredump.c:297:56: error: suggest braces around empty body in an 'if' statement [-Werror=empty-body]
  297 |                 /* nothing - symlink will be missing */;
      |                                                        ^
drivers/base/devcoredump.c:301:56: error: suggest braces around empty body in an 'if' statement [-Werror=empty-body]
  301 |                 /* nothing - symlink will be missing */;
      |                                                        ^

Randy tried addressing this one before, and there were multiple
other ideas in that thread.

Add a runtime warning and code comment here.

Link: https://lore.kernel.org/lkml/20200418184111.13401-8-rdunlap@infradead.org/
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Link: https://lore.kernel.org/r/20210322114258.3420937-1-arnd@kernel.orgSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/base/devcoredump.c

@@ -292,13 +292,16 @@ void dev_coredumpm(struct device *dev, struct module *owner,
 	if (device_add(&devcd->devcd_dev))
 		goto put_device;
 
+	/*
+	 * These should normally not fail, but there is no problem
+	 * continuing without the links, so just warn instead of
+	 * failing.
+	 */
 	if (sysfs_create_link(&devcd->devcd_dev.kobj, &dev->kobj,
-			      "failing_device"))
-		/* nothing - symlink will be missing */;
-
-	if (sysfs_create_link(&dev->kobj, &devcd->devcd_dev.kobj,
-			      "devcoredump"))
-		/* nothing - symlink will be missing */;
+			      "failing_device") ||
+	    sysfs_create_link(&dev->kobj, &devcd->devcd_dev.kobj,
+		              "devcoredump"))
+		dev_warn(dev, "devcoredump create_link failed\n");
 
 	INIT_DELAYED_WORK(&devcd->del_wk, devcd_del);
 	schedule_delayed_work(&devcd->del_wk, DEVCD_TIMEOUT);