bcachefs: Fix sysfs rebalance duration waited formatting

cat /sys/fs/bcachefs/*/internal/rebalance_status
waiting
  io wait duration:  13.5 GiB
  io wait remaining: 627 MiB
  duration waited:   1392 m

duration waited was increasing at a rate of about 14 times the expected
rate.

div_u64 takes a u32 divisor, but u->nsecs (from time_units[]) can be
bigger than u32.
Signed-off-by: Feiko Nanninga <feiko.nanninga@fnanninga.de>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/util.c

@@ -360,7 +360,7 @@ void bch2_pr_time_units(struct printbuf *out, u64 ns)
 {
 	const struct time_unit *u = bch2_pick_time_units(ns);
 
-	prt_printf(out, "%llu %s", div_u64(ns, u->nsecs), u->name);
+	prt_printf(out, "%llu %s", div64_u64(ns, u->nsecs), u->name);
 }
 
 static void bch2_pr_time_units_aligned(struct printbuf *out, u64 ns)