percpu: make percpu symbols in tracer unique

This patch updates percpu related symbols in kernel tracer such that
percpu symbols are unique and don't clash with local symbols.  This
serves two purposes of decreasing the possibility of global percpu
symbol collision and allowing dropping per_cpu__ prefix from percpu
symbols.

* kernel/trace/trace.c: s/max_data/max_tr_data/
* kernel/trace/trace_hw_branches: s/tracer/hwb_tracer/, s/buffer/hwb_buffer/

Partly based on Rusty Russell's "alloc_percpu: rename percpu vars
which cause name clashes" patch.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@redhat.com>
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 8439cdc..85a5ed7 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -203,7 +203,7 @@
  */
 static struct trace_array	max_tr;
 
-static DEFINE_PER_CPU(struct trace_array_cpu, max_data);
+static DEFINE_PER_CPU(struct trace_array_cpu, max_tr_data);
 
 /* tracer_enabled is used to toggle activation of a tracer */
 static int			tracer_enabled = 1;
@@ -4426,7 +4426,7 @@
 	/* Allocate the first page for all buffers */
 	for_each_tracing_cpu(i) {
 		global_trace.data[i] = &per_cpu(global_trace_cpu, i);
-		max_tr.data[i] = &per_cpu(max_data, i);
+		max_tr.data[i] = &per_cpu(max_tr_data, i);
 	}
 
 	trace_init_cmdlines();