ethdev: remove inclusion of mbuf header

The ethdev header file includes the mbuf header file, but it does not
need to do so as it only uses pointers to the struct rte_mbuf type, and
does not use any of the mbuf internals, nor any of the mbuf functions or
macros. Therefore the inclusion is unnecessary, and can be replaced by a
forward declaration of the mbuf type.

Signed-off-by: Bruce Richardson <bruce.richardson@intel.com>
Acked-by: Olivier Matz <olivier.matz@6wind.com>

lib/librte_ether/rte_ethdev.h

@@ -180,10 +180,11 @@ extern "C" {
 #include <rte_pci.h>
 #include <rte_dev.h>
 #include <rte_devargs.h>
-#include <rte_mbuf.h>
 #include "rte_ether.h"
 #include "rte_eth_ctrl.h"
 
+struct rte_mbuf;
+
 /**
  * A structure used to retrieve statistics for an Ethernet port.
  */