cyassl: upgrade to v2.8.0

Un-reverts the previous update commit and forward-ports the patch
to improve legacy SSLv2 handshake handling.

Signed-off-by: Jo-Philipp Wich <jow@openwrt.org>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@38609 3c298f89-4303-0410-b956-a3cf2f4a3e73