move unix_file_* code to vppinfra

This will allow us to use this code in client libraries without vlib.

Change-Id: I8557b752496841ba588aa36b6082cbe2cd1867fe
Signed-off-by: Damjan Marion <damarion@cisco.com>
diff --git a/src/vnet/devices/netmap/netmap.h b/src/vnet/devices/netmap/netmap.h
index e04f045..0473189 100644
--- a/src/vnet/devices/netmap/netmap.h
+++ b/src/vnet/devices/netmap/netmap.h
@@ -50,7 +50,7 @@
   uword if_index;
   u32 hw_if_index;
   u32 sw_if_index;
-  u32 unix_file_index;
+  u32 clib_file_index;
 
   u32 per_interface_next_index;
   u8 is_admin_up;