Remove workaround for unimmunized rcu_dereference from mce_log()

Remove the rmb() from mce_log(), since the immunized version of
rcu_dereference() makes it unnecessary.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Andi Kleen <ak@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/x86/kernel/mce_64.c

@@ -76,9 +76,6 @@ void mce_log(struct mce *mce)
 	wmb();
 	for (;;) {
 		entry = rcu_dereference(mcelog.next);
-		/* The rmb forces the compiler to reload next in each
-		    iteration */
-		rmb();
 		for (;;) {
 			/* When the buffer fills up discard new entries. Assume
 			   that the earlier errors are the more interesting. */