lksctp-tools: add ptest subpackage and other updates

Some updates for lksctp-tools:

* add ptest subpackage
* only blacklist lksctp-tools when gold ld is used. Refer to:
https://bugs.gentoo.org/show_bug.cgi?id=530318


* update licenses and add homepage.

Signed-off-by: Kai Kang <kai.kang@windriver.com>
Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>