[Blackfin] arch: disable bfin_get_ether_addr fucntion for boards when do not use MAC driver

Signed-off-by: Martin Strubel <hackfin@section5.ch>
Signed-off-by: Bryan Wu <bryan.wu@analog.com>

arch/blackfin/mach-bf537/boards/generic_board.c

@@ -733,9 +733,11 @@ void native_machine_restart(char *cmd)
 		bfin_gpio_reset_spi0_ssel1();
 }
 
+#if defined(CONFIG_BFIN_MAC) || defined(CONFIG_BFIN_MAC_MODULE)
 void bfin_get_ether_addr(char *addr)
 {
 	random_ether_addr(addr);
 	printk(KERN_WARNING "%s:%s: Setting Ethernet MAC to a random one\n", __FILE__, __func__);
 }
 EXPORT_SYMBOL(bfin_get_ether_addr);
+#endif