Enable sha512sum

Makefile

@@ -162,6 +162,7 @@ config: FORCE
 	echo \
 		'CONFIG_TARGET_$(BOARD)=y' \
 		'CONFIG_TARGET_ROOTFS_JFFS2=n' \
+		'CONFIG_BUSYBOX_CONFIG_SHA512SUM=y' \
 		'CONFIG_ATH_USER_REGD=y' \
 		'$(patsubst %,CONFIG_PACKAGE_%=m,$(sort $(GLUON_DEFAULT_PACKAGES) $(GLUON_SITE_PACKAGES) $(PROFILE_PACKAGES)))' \
 		| sed -e 's/ /\n/g' > .config