misc: vmw_balloon: fix memory leak with using debugfs_lookup()

When calling debugfs_lookup() the result must have dput() called on it,
otherwise the memory will leak over time. To make things simpler, just
call debugfs_lookup_and_remove() instead which handles all of the logic at
once.

Cc: Nadav Amit <[e-mail]>
Cc: VMware PV-Drivers Reviewers <[e-mail]>
Cc: Arnd Bergmann <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/misc/vmw_balloon.c

···
 static void __exit vmballoon_debugfs_exit(struct vmballoon *b)
 {
 	static_key_disable(&balloon_stat_enabled.key);
-	debugfs_remove(debugfs_lookup("vmmemctl", NULL));
+	debugfs_lookup_and_remove("vmmemctl", NULL);
 	kfree(b->stats);
 	b->stats = NULL;
 }