Introduce netdev.h header file and remove externs

This addresses all drivers whose initializers have already
been moved to board_eth_init()/cpu_eth_init().

Signed-off-by: Ben Warren <biggerbadderben@gmail.com>
diff --git a/cpu/mcf5445x/cpu.c b/cpu/mcf5445x/cpu.c
index ab342dd..a30c327 100644
--- a/cpu/mcf5445x/cpu.c
+++ b/cpu/mcf5445x/cpu.c
@@ -28,6 +28,7 @@
 #include <common.h>
 #include <watchdog.h>
 #include <command.h>
+#include <netdev.h>
 
 #include <asm/immap.h>
 
@@ -102,8 +103,6 @@
  * 	int board_eth_init(bd_t *bis)
  */
 
-extern int mcffec_initialize(bd_t*);
-
 int cpu_eth_init(bd_t *bis)
 {
 	return mcffec_initialize(bis);