trace_kprobe: Remove warning message "Could not insert probe at..."

This warning message is not very helpful, as the return value should
already show information about the error. Also, this message will
spam dmesg if the user space does testing in a loop, like:

    for x in {0..5}
    do
        echo p:xx xx+$x >> /sys/kernel/debug/tracing/kprobe_events
    done

Reported-by: Vince Weaver <vincent.weaver@maine.edu>
Signed-off-by: Song Liu <songliubraving@fb.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: kernel-team@fb.com
Link: http://lkml.kernel.org/r/20180413185513.3626052-1-songliubraving@fb.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

kernel/trace/trace_kprobe.c

@@ -512,8 +512,6 @@ static int __register_trace_kprobe(struct trace_kprobe *tk)
 	if (ret == 0)
 		tk->tp.flags |= TP_FLAG_REGISTERED;
 	else {
-		pr_warn("Could not insert probe at %s+%lu: %d\n",
-			trace_kprobe_symbol(tk), trace_kprobe_offset(tk), ret);
 		if (ret == -ENOENT && trace_kprobe_is_on_module(tk)) {
 			pr_warn("This probe might be able to register after target module is loaded. Continue.\n");
 			ret = 0;