microblaze: Do not select NFS for platforms without ethernet

Undefined network functionality for systems without ethernet
and disable NFS support.

Signed-off-by: Michal Simek <monstr@monstr.eu>

include/configs/microblaze-generic.h

@@ -60,6 +60,7 @@
 /*#define	CONFIG_SYS_RESET_ADDRESS	CONFIG_SYS_TEXT_BASE*/
 
 /* ethernet */
+#undef CONFIG_SYS_ENET
 #ifdef XILINX_EMACLITE_BASEADDR
 # define CONFIG_XILINX_EMACLITE		1
 # define CONFIG_SYS_ENET
@@ -243,6 +244,7 @@
 #ifndef CONFIG_SYS_ENET
 # undef CONFIG_CMD_NET
 # undef CONFIG_NET_MULTI
+# undef CONFIG_CMD_NFS
 #else
 # define CONFIG_CMD_PING
 # define CONFIG_CMD_DHCP