tracing: Simplify conditional compilation code in tracing_set_tracer()

Two conditional compilation directives "#ifdef CONFIG_TRACER_MAX_TRACE"
are used consecutively, and no other code in between. Simplify conditional
the compilation code and only use one "#ifdef CONFIG_TRACER_MAX_TRACE".

Link: https://lkml.kernel.org/r/20220602140613.545069-1-sunliming@kylinos.cn



Signed-off-by: sunliming <sunliming@kylinos.cn>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>