tracing: Remove __idx variable from __DO_TRACE

Since the removal of SRCU-protected tracepoints, the __idx variable in
__DO_TRACE is unused. Remove this variable.

Fixes: 48bcda684823 ("tracing: Remove definition of trace_*_rcuidle()")
Cc: Linus Torvalds <[e-mail]>
Cc: Thomas Gleixner <[e-mail]>
Cc: Michael Jeanson <[e-mail]>
Cc: Masami Hiramatsu <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Cc: Alexei Starovoitov <[e-mail]>
Cc: Yonghong Song <[e-mail]>
Cc: Paul E. McKenney <[e-mail]>
Cc: Ingo Molnar <[e-mail]>
Cc: Arnaldo Carvalho de Melo <[e-mail]>
Cc: Mark Rutland <[e-mail]>
Cc: Alexander Shishkin <[e-mail]>
Cc: Namhyung Kim <[e-mail]>
Cc: Andrii Nakryiko <[e-mail]>
Cc: [e-mail]
Cc: Joel Fernandes <[e-mail]>
Cc: Jordan Rife <[e-mail]>
Link: https://lore.kernel.org/[e-mail]
Signed-off-by: Mathieu Desnoyers <[e-mail]>
Signed-off-by: Steven Rostedt (Google) <[e-mail]>

include/linux/tracepoint.h

···
  */
 #define __DO_TRACE(name, args, cond, syscall)				\
 	do {								\
-		int __maybe_unused __idx = 0;				\
-									\
 		if (!(cond))						\
 			return;						\
 									\