ftrace: sample: avoid open-coded 64-bit division

Calculating the average period requires a 64-bit division that leads
to a link failure on 32-bit architectures:

x86_64-linux-ld: samples/ftrace/ftrace-ops.o: in function `ftrace_ops_sample_init':
ftrace-ops.c:(.init.text+0x23b): undefined reference to `__udivdi3'

Use the div_u64() helper to do this instead. Since this is an init function that
is not called frequently, the runtime overhead is going to be acceptable.

Link: https://lore.kernel.org/linux-trace-kernel/[e-mail]

Cc: Masami Hiramatsu <[e-mail]>
Fixes: b56c68f705ca ("ftrace: Add sample with custom ops")
Signed-off-by: Arnd Bergmann <[e-mail]>
Acked-by: Mark Rutland <[e-mail]>
Signed-off-by: Steven Rostedt (Google) <[e-mail]>

samples/ftrace/ftrace-ops.c

···
 
 	pr_info("Attempted %u calls to %ps in %lluns (%lluns / call)\n",
 		nr_function_calls, tracee_relevant,
-		period, period / nr_function_calls);
+		period, div_u64(period, nr_function_calls));
 
 	if (persist)
 		return 0;