Remove support for BSD version of PolarSSL

"The BSD version of PolarSSL was made for migratory purposes only and is not
maintained. The GPL version of PolarSSL is actually the only actively
developed version, so I would be very reluctant to use the BSD version." /
Paul Bakker, PolarSSL hacker.

Signed-off-by: Hoi-Ho Chan <hoiho.chan@gmail.com>