build librpc and remove unused NTP_SERVER

librpc isn't included with cm-10.1 branch of qcom/gps

NTP_SERVER is remove because platform now uses Settings.Secure.NTP_SERVER.

Tuna commit: https://github.com/CyanogenMod/android_device_samsung_tuna/commit/415a1796581b508d39f1b2152288ff70b25a17c7

Change-Id: Ie3ab405cd1d653207fcaa4fd0eec6eef088373c7