L2-input: use vlib_buffer_enqueue_to_next

use the same trick as l2-ouput to group the processing of packets
on the same interface.

Change-Id: Ib2a6a1b5f362372936197f5bb2fdd0fe9439226b
Signed-off-by: Neale Ranns <nranns@cisco.com>
diff --git a/src/vnet/ethernet/packet.h b/src/vnet/ethernet/packet.h
index d70960b..04ce420 100644
--- a/src/vnet/ethernet/packet.h
+++ b/src/vnet/ethernet/packet.h
@@ -64,20 +64,20 @@
 
 /* I/G bit: individual (unicast)/group (broadcast/multicast). */
 always_inline uword
-ethernet_address_cast (u8 * a)
+ethernet_address_cast (const u8 * a)
 {
   return (a[0] >> 0) & 1;
 }
 
 always_inline int
-ethernet_address_is_broadcast (u8 * a)
+ethernet_address_is_broadcast (const u8 * a)
 {
   return clib_mem_unaligned (a, u32) == 0xffffffff &&
     clib_mem_unaligned (a + 4, u16) == 0xffff;
 }
 
 always_inline uword
-ethernet_address_is_locally_administered (u8 * a)
+ethernet_address_is_locally_administered (const u8 * a)
 {
   return (a[0] >> 1) & 1;
 }