Telephony: Add data rat constant

This event constant is used in DcTracker

Change-Id: I1f9b34a8689c43c2586e9e3a92f0453649775d73
(cherry picked from commit f7ca98035479b670ff51bc9298fd7928a5e0f80d)
(cherry picked from commit f4d8f7b8fa390302b9cc51a5640e017ff393dfcc)
(cherry picked from commit 77d810390fbca8cb1d10bce148035fada414e0eb)