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/mcf52x2/cpu.c b/cpu/mcf52x2/cpu.c
index 2af31cb..167097a 100644
--- a/cpu/mcf52x2/cpu.c
+++ b/cpu/mcf52x2/cpu.c
@@ -32,6 +32,7 @@
 #include <watchdog.h>
 #include <command.h>
 #include <asm/immap.h>
+#include <netdev.h>
 
 #ifdef  CONFIG_M5271
 /*
@@ -328,8 +329,6 @@
  * 	int board_eth_init(bd_t *bis)
  */
 
-extern int mcffec_initialize(bd_t*);
-
 int cpu_eth_init(bd_t *bis)
 {
 	return mcffec_initialize(bis);