microblaze: Fix EMAC Lite initialization

It is possible for CONFIG_XILINX_EMACLITE to be defined without
XILINX_EMACLITE_BASEADDR being defined as the EMAC Lite driver support
OF init. Check that the driver is enabled and the base address is
available before initializing with a static base address.

Signed-off-by: Nathan Rossi <nathan.rossi@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>

board/xilinx/microblaze-generic/microblaze-generic.c

@@ -109,7 +109,7 @@ int board_eth_init(bd_t *bis)
 						XILINX_AXIDMA_BASEADDR);
 #endif
 
-#ifdef CONFIG_XILINX_EMACLITE
+#if defined(CONFIG_XILINX_EMACLITE) && defined(XILINX_EMACLITE_BASEADDR)
 	u32 txpp = 0;
 	u32 rxpp = 0;
 # ifdef CONFIG_XILINX_EMACLITE_TX_PING_PONG