net: phy.h: Make PHY autonegotiation timeout configurable

The Marvell MV78460 eval board DB-78460-BP seems to need a longer
PHY autonegotiation timeout than the "standard" 4 seconds. So lets
make this timeout configurable. If not defined in the board config
header the original 4000ms is used.
Signed-off-by: NStefan Roese <sr@denx.de>
Cc: Joe Hershberger <joe.hershberger@gmail.com>

include/phy.h

@@ -32,7 +32,9 @@
 #define PHY_10G_FEATURES	(PHY_GBIT_FEATURES | \
 				SUPPORTED_10000baseT_Full)
 
+#ifndef PHY_ANEG_TIMEOUT
 #define PHY_ANEG_TIMEOUT	4000
+#endif
 
 
 typedef enum {