Add dm-mod and dm-crypt kernel modules to support encrypted disk image

Change-Id: Ifeee5a83c70e67ad37e7fb5d6378c5023fb45a28
diff --git a/debian/defconfig b/debian/defconfig
index 9988a03..238c9e8 100644
--- a/debian/defconfig
+++ b/debian/defconfig
@@ -90,3 +90,7 @@
 CONFIG_I2C_MUX_PCA954x=m
 CONFIG_INPUT_TOUCHSCREEN=y
 CONFIG_TOUCHSCREEN_SEC_TS_1223=m
+
+CONFIG_MD=y
+CONFIG_BLK_DEV_DM=m
+CONFIG_DM_CRYPT=m