RIL_UNSOL_MODEM_RESTART will be sent by vendor RILs when it detects a modem restart along with the reason for restart which could be a crash signature if the modem restarted due to a crash or a some other string such as a user-initiated restart or AT command initiated restart. Change-Id: Idf08e20a49e82d40f6aa0854d23384c35c2efc3a