E1000: clean up CONFIG_E1000_FALLBACK_MAC handling

Avoid "integer constant is too large for 'long' type" warnings.
And simplify the code.

Signed-off-by: Wolfgang Denk <wd@denx.de>
diff --git a/include/configs/MVBC_P.h b/include/configs/MVBC_P.h
index ff6f6cc..48f427e 100644
--- a/include/configs/MVBC_P.h
+++ b/include/configs/MVBC_P.h
@@ -255,7 +255,7 @@
 #define CONFIG_NET_RETRY_COUNT 5
 
 #define CONFIG_E1000
-#define CONFIG_E1000_FALLBACK_MAC	0xb6b445ebfbc0
+#define CONFIG_E1000_FALLBACK_MAC	{ 0xb6, 0xb4, 0x45, 0xeb, 0xfb, 0xc0 }
 #undef CONFIG_MPC5xxx_FEC
 #undef CONFIG_PHY_ADDR
 #define CONFIG_NETDEV		eth0