PPC: Drop mv6436x_eth_initialize() from net/eth.c

This function was defined as an extern in net/eth.c, drop that and use
standard means of calling it.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Reinhard Arlt <reinhard.arlt@esd-electronics.com>
diff --git a/board/Marvell/db64360/eth.h b/board/Marvell/db64360/eth.h
index aab32d2..6fbfdfe 100644
--- a/board/Marvell/db64360/eth.h
+++ b/board/Marvell/db64360/eth.h
@@ -39,5 +39,6 @@
 void db64360_eth0_disable(void);
 bool network_start(bd_t *bis);
 
+int mv6436x_eth_initialize(bd_t *);
 
 #endif /* __EVB64360_ETH_H__ */