tracing/probes: Integrate duplicate set_print_fmt()

The set_print_fmt() functions are implemented almost same for
[ku]probes.  Move it to a common place and get rid of the duplication.

Acked-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: zhangwei(Jovi) <jovi.zhangwei@huawei.com>
Cc: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>

kernel/trace/trace_probe.h

@@ -226,3 +226,5 @@ store_trace_args(int ent_size, struct trace_probe *tp, struct pt_regs *regs,
 				   data + tp->args[i].offset);
 	}
 }
+
+extern int set_print_fmt(struct trace_probe *tp, bool is_return);