board: tbs2910: Remove CMD_FDT support in defconfig to reduce u-boot size

This fixes the build failure "u-boot.imx exceeds file size limit".

Signed-off-by: Soeren Moch <smoch@web.de>
diff --git a/configs/tbs2910_defconfig b/configs/tbs2910_defconfig
index 05973ea..96b813d 100644
--- a/configs/tbs2910_defconfig
+++ b/configs/tbs2910_defconfig
@@ -15,6 +15,7 @@
 CONFIG_HUSH_PARSER=y
 CONFIG_SYS_PROMPT="Matrix U-Boot> "
 CONFIG_CMD_BOOTZ=y
+# CONFIG_CMD_FDT is not set
 CONFIG_CMD_MEMTEST=y
 # CONFIG_CMD_FLASH is not set
 CONFIG_CMD_GPIO=y