Add support for sending message with priority, link control and validity period options

1. Added support for message priority(indicates the priority of a
   SMS to the network in the PDU) in 3gpp2
2. Added support for link control(indicates whether network can
   expect more messages or not so it can decide whether to retain
   the radio link or not) while sending multiple messages
3. Added support for validity period(indicates how much time the
   SMS is valid at the SMSC) support in 3gpp
4. Amended UT test cases for API changes and add UT validity period
   test case

Test: Verfied sending short SMS, long SMS, MMS, SMS with emoji on
      live network

Change-Id: I53bb027531959f71285e5f79896768a591129536
CRs-Fixed: 2177389