defconfig: sdm670: enable default key driver

Enable default key driver to support metadata encryption.
File system metadata will be encrypted with a default
key generated during bootup.

Change-Id: If65c986dcf5e9a8295cb43ae37aae55fcb06f1be
Signed-off-by: Neeraj Soni <neersoni@codeaurora.org>
diff --git a/arch/arm64/configs/sdm670_defconfig b/arch/arm64/configs/sdm670_defconfig
index 747d373..a4363ac9 100644
--- a/arch/arm64/configs/sdm670_defconfig
+++ b/arch/arm64/configs/sdm670_defconfig
@@ -279,6 +279,7 @@
 CONFIG_BLK_DEV_DM=y
 CONFIG_DM_CRYPT=y
 CONFIG_DM_REQ_CRYPT=y
+CONFIG_DM_DEFAULT_KEY=y
 CONFIG_DM_UEVENT=y
 CONFIG_DM_VERITY=y
 CONFIG_DM_VERITY_FEC=y