tracing: Move it_func[0] comment to the relevant context

When introducing __DO_TRACE_CALL(), the iteration over it_func moved
from __DO_TRACE() to __tracepoint_iter_##_name(), but the comment
relevant for this iterator was left in its original location.

Move the comment to the relevant context.

Fixes: d25e37d ("tracepoint: Optimize using static_call()")
Cc: Linus Torvalds <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Michael Jeanson <[email protected]>
Cc: Masami Hiramatsu <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Alexei Starovoitov <[email protected]>
Cc: Yonghong Song <[email protected]>
Cc: Paul E. McKenney <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Arnaldo Carvalho de Melo <[email protected]>
Cc: Mark Rutland <[email protected]>
Cc: Alexander Shishkin <[email protected]>
Cc: Namhyung Kim <[email protected]>
Cc: Andrii Nakryiko <[email protected]>
Cc: [email protected]
Cc: Joel Fernandes <[email protected]>
Cc: Jordan Rife <[email protected]>
Link: https://lore.kernel.org/[email protected]
Signed-off-by: Mathieu Desnoyers <[email protected]>
Signed-off-by: Steven Rostedt (Google) <[email protected]>

Author: compudj

include/linux/tracepoint.h

@@ -210,9 +210,6 @@ static inline struct tracepoint *tracepoint_ptr_deref(tracepoint_ptr_t *p)
 #endif /* CONFIG_HAVE_STATIC_CALL */
 
 /*
- * it_func[0] is never NULL because there is at least one element in the array
- * when the array itself is non NULL.
- *
  * With @syscall=0, the tracepoint callback array dereference is
  * protected by disabling preemption.
  * With @syscall=1, the tracepoint callback array dereference is
@@ -316,6 +313,9 @@ static inline struct tracepoint *tracepoint_ptr_deref(tracepoint_ptr_t *p)
  * We have no guarantee that gcc and the linker won't up-align the tracepoint
  * structures, so we create an array of pointers that will be used for iteration
  * on the tracepoints.
+ *
+ * it_func[0] is never NULL because there is at least one element in the array
+ * when the array itself is non NULL.
  */
 #define __DEFINE_TRACE_EXT(_name, _ext, proto, args)			\
 	static const char __tpstrtab_##_name[]				\