Remove SPL undefine of CONFIG_OF_CONTROL

Allow SPL to be built with this option so that we can support device tree
control. Disable the simple bus for now in SPL. It may be needed later.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/include/config_uncmd_spl.h b/include/config_uncmd_spl.h
index 38cb0e8..c191f56 100644
--- a/include/config_uncmd_spl.h
+++ b/include/config_uncmd_spl.h
@@ -20,7 +20,9 @@
 #undef CONFIG_CMD_SNTP
 #undef CONFIG_CMD_TFTPPUT
 #undef CONFIG_CMD_TFTPSRV
+#ifdef CONFIG_SPL_DISABLE_OF_CONTROL
 #undef CONFIG_OF_CONTROL
+#endif
 
 #ifndef CONFIG_SPL_DM
 #undef CONFIG_DM_SERIAL