build: add urandom-seed and urngd to default packages set

urandom-seed content was split from base-files into separate package so
in order to preserve the current functionality and to provide some
fallback mechanism in case jent-rng initialization fails in urngd we
need to add it back.

urngd is OpenWrt's micro non-physical true random number generator based
on timing jitter.

Tested-by: Lucian Cristian <lucian.cristian@gmail.com>
Signed-off-by: Petr Štetiar <ynezz@true.cz>
(cherry picked from commit f5387b754f98f85bf4a1c8c392a965bdbcb96db6)

include/target.mk

@@ -13,7 +13,7 @@ __target_inc=1
 DEVICE_TYPE?=router
 
 # Default packages - the really basic set
-DEFAULT_PACKAGES:=base-files libc libgcc busybox dropbear mtd uci opkg netifd fstools uclient-fetch logd
+DEFAULT_PACKAGES:=base-files libc libgcc busybox dropbear mtd uci opkg netifd fstools uclient-fetch logd urandom-seed urngd
 # For nas targets
 DEFAULT_PACKAGES.nas:=block-mount fdisk lsblk mdadm
 # For router targets