blackfin: replace bfin_gen_rand_mac() with eth_random_addr()

bfin_gen_rand_mac() uses __DATE__ as the seed for random ethernet
address. This makes the build non-deterministic.

In the first place, it should not be implemented as a Bfin-specific
function. Use eth_random_addr() instead.

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
Cc: Sonic Zhang <sonic.zhang@analog.com>
diff --git a/include/configs/ip04.h b/include/configs/ip04.h
index 0efa2b7..3767502 100644
--- a/include/configs/ip04.h
+++ b/include/configs/ip04.h
@@ -77,6 +77,7 @@
 #define DM9000_IO		CONFIG_DM9000_BASE
 #define DM9000_DATA		(CONFIG_DM9000_BASE + 2)
 
+#define CONFIG_LIB_RAND
 
 /*
  * Flash Settings