update setup_env.sh shell script, add install libssl-dev for dtc

guowenxue

2019-09-23 c35ac6f2aad2ebe9d7cb5ca461822f0635af3798

linux-bsp/tarballs/linux-at91.tar.xz does not exist in tree cd5daf75af4be0220d90a38c41d13205196f4996