tracing: Move ftrace_max_lock into trace_array

In preparation for having tracers enabled in instances, the max_lock
should be unique as updating the max for one tracer is a separate
operation than updating it for another tracer using a different max.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

diff --cc kernel/trace/trace.c
Simple merge

diff --cc kernel/trace/trace.h
Simple merge

diff --cc kernel/trace/trace_selftest.c
Simple merge