check for "/mtd_rwarea/dropbear_rsa_host_key" key file, if it exist , use it, if it doesn't exist, than generate one via dropbearkey -t rsa -f $KEY_FILE
other file wich is "/mtd_rwarea/authorized_keys" holds host's key for later use i guess

You can use this script from /mtd_rwarea directly if your path has dropbear or via adding path of dropbears to required lines.
