vlib: retrieve the root bus of a given pci device

Added a function to parse sysfs, determine the root bus & domain of a given pci
device.

Type: improvement

Signed-off-by: Ray Kinsella <mdr@ashroe.eu>
Change-Id: I36778116ecaa2d591617450fe5ae0bdb46b4424b
diff --git a/src/vlib/pci/pci.c b/src/vlib/pci/pci.c
index 18d93ac..5535eb1 100644
--- a/src/vlib/pci/pci.c
+++ b/src/vlib/pci/pci.c
@@ -61,6 +61,12 @@
   return 0;
 }
 
+clib_error_t *__attribute__ ((weak))
+vlib_pci_get_device_root_bus (vlib_pci_addr_t *addr, vlib_pci_addr_t *root_bus)
+{
+  return 0;
+}
+
 vlib_pci_addr_t * __attribute__ ((weak)) vlib_pci_get_all_dev_addrs ()
 {
   return 0;