oom: remove references to old badness() function

The badness() function in the oom killer was renamed to oom_badness() in
a63d83f427fb ("oom: badness heuristic rewrite") since it is a globally
exported function for clarity.

The prototype for the old function still existed in linux/oom.h, so remove
it.  There are no existing users.

Also fixes documentation and comment references to badness() and adjusts
them accordingly.

Signed-off-by: David Rientjes <rientjes@google.com>
Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/Documentation/feature-removal-schedule.txt b/Documentation/feature-removal-schedule.txt
index f9d240df..d093e55 100644
--- a/Documentation/feature-removal-schedule.txt
+++ b/Documentation/feature-removal-schedule.txt
@@ -184,7 +184,7 @@
 
 	A much more powerful interface, /proc/<pid>/oom_score_adj, was
 	introduced with the oom killer rewrite that allows users to increase or
-	decrease the badness() score linearly.  This interface will replace
+	decrease the badness score linearly.  This interface will replace
 	/proc/<pid>/oom_adj.
 
 	A warning will be emitted to the kernel log if an application uses this