board: gdsys: Remove commands to reduce footprint

Commit "2842c1c fit: add sha256 support" badly increased
memory footprint, so some of our boards did not build anymore.
Since monitor base must not be changed I removed some commands
to save memory.

Maybe making sha256 optional for fit would be an option for
the future since it really has some beefy footprint.

Signed-off-by: Dirk Eibach <dirk.eibach@gdsys.cc>
diff --git a/include/configs/iocon.h b/include/configs/iocon.h
index 1836d12..35ba1bd 100644
--- a/include/configs/iocon.h
+++ b/include/configs/iocon.h
@@ -64,6 +64,10 @@
 #define CONFIG_CMD_CACHE
 #define CONFIG_CMD_FPGAD
 #undef CONFIG_CMD_EEPROM
+#undef CONFIG_CMD_ELF
+#undef CONFIG_CMD_I2C
+#undef CONFIG_CMD_IRQ
+#undef CONFIG_CMD_NFS
 
 /*
  * SDRAM configuration (please see cpu/ppc/sdram.[ch])