bfd: add missing cast

Add missing cast to time conversion function to to deal with arbitrary
clocks-per-second values.

Type: fix

Change-Id: I5075a823e7a95c972c513ac765252337d5f59fbf
Signed-off-by: Klement Sekera <ksekera@cisco.com>
diff --git a/src/vnet/bfd/bfd_main.c b/src/vnet/bfd/bfd_main.c
index ef6ada8..34e9804 100644
--- a/src/vnet/bfd/bfd_main.c
+++ b/src/vnet/bfd/bfd_main.c
@@ -60,7 +60,7 @@
 u32
 bfd_clocks_to_usec (const bfd_main_t * bm, u64 clocks)
 {
-  return (clocks / bm->cpu_cps) * USEC_PER_SECOND;
+  return ((f64) clocks / bm->cpu_cps) * USEC_PER_SECOND;
 }
 
 static vlib_node_registration_t bfd_process_node;