uprobes: Fix misleading log entry

There don't have any 'r' prefix in uprobe event naming, remove it.
Signed-off-by: Jovi Zhang <bookjovi@gmail.com>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>

kernel/trace/trace_uprobe.c

@@ -189,7 +189,7 @@ static int create_trace_uprobe(int argc, char **argv)
 	if (argv[0][0] == '-')
 		is_delete = true;
 	else if (argv[0][0] != 'p') {
-		pr_info("Probe definition must be started with 'p', 'r' or" " '-'.\n");
+		pr_info("Probe definition must be started with 'p' or '-'.\n");
 		return -EINVAL;
 	}