imx6: aristainetos: add thumb build

add thumb build to aristainetos build to save
binary space.

Signed-off-by: Heiko Schocher <hs@denx.de>
diff --git a/configs/aristainetos2_defconfig b/configs/aristainetos2_defconfig
index bc18786..eda05a4 100644
--- a/configs/aristainetos2_defconfig
+++ b/configs/aristainetos2_defconfig
@@ -1,4 +1,5 @@
 CONFIG_ARM=y
+CONFIG_SYS_THUMB_BUILD=y
 CONFIG_ARCH_MX6=y
 CONFIG_SYS_TEXT_BASE=0x17800000
 CONFIG_TARGET_ARISTAINETOS2=y