buildroot

libpjsip: fix ssl support

Currently, ssl support is implicitely disabled in the initial configure
options. This overrides the check for openssl below.

libpjsip is also currently only compatible with libopenssl. Change
the check to LIBOPENSSL instead of openssl, and depend on libopenssl.

Signed-off-by: Adam Duskett <aduskett@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>