vf610twr: Enable thumb2 for builds

To help with size constraints, enable thumb2 when building.

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/vf610twr_defconfig b/configs/vf610twr_defconfig
index 3f38c88..a928cd4 100644
--- a/configs/vf610twr_defconfig
+++ b/configs/vf610twr_defconfig
@@ -1,4 +1,6 @@
 CONFIG_ARM=y
+CONFIG_SYS_THUMB_BUILD=y
+# CONFIG_SPL_SYS_THUMB_BUILD is not set
 CONFIG_ARCH_VF610=y
 CONFIG_SYS_TEXT_BASE=0x3f401000
 CONFIG_NR_DRAM_BANKS=1