Add Constants for NATT Keepalive to RILConstants

Bug: 38350389
Test: compilation
Merged-In: Ic18a7c947d2c62efe76d656bd683f9ce296f68fd
Change-Id: Ic18a7c947d2c62efe76d656bd683f9ce296f68fd
(cherry picked from commit 974aada04734ced17f3842c817e7e8c3528d0739)
1 file changed