tracing: Drop unused helper function to fix the build

A helper function defined but not used. This, in particular,
prevents kernel builds with clang, `make W=1` and CONFIG_WERROR=y:

kernel/trace/trace.c:2229:19: error: unused function 'run_tracer_selftest' [-Werror,-Wunused-function]
 2229 | static inline int run_tracer_selftest(struct tracer *type)
      |                   ^~~~~~~~~~~~~~~~~~~

Fix this by dropping unused functions.

See also commit 6863f56 ("kbuild: allow Clang to find unused static
inline functions for W=1 build").

Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Bill Wendling <morbo@google.com>
Cc: Justin Stitt <justinstitt@google.com>
Link: https://lore.kernel.org/20240909105314.928302-1-andriy.shevchenko@linux.intel.com
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

Author: andy-shev

kernel/trace/trace.c

@@ -2226,10 +2226,6 @@ static __init int init_trace_selftests(void)
 }
 core_initcall(init_trace_selftests);
 #else
-static inline int run_tracer_selftest(struct tracer *type)
-{
-	return 0;
-}
 static inline int do_run_tracer_selftest(struct tracer *type)
 {
 	return 0;