ppp: remove ppp requirement from chat

This patch removes dependancy of PPP from chat application as chat application can be used for other serial communication as well that is not dependant on PPP and therefore one should be able to install chat without PPP. There also are no dependencies within chat application for PPP.

Signed-off-by: Oskari Rauta <oskari.rauta at gmail.com>

SVN-Revision: 39992