get smsc with phone identitiy to send message

Get smsc with phone identitiy to send message to
fill sms packet. No need to use caller privileges
here as the intention is to get it if caller
passed null. This will avoid throwing
security exception for apps with only SMS permission
for not having read privileged permission.

Bug: 274708908
Test: NoReceiveSmsPermissionTest
Change-Id: I4ba49166d4872e53fdc6fee0c1a5d7eab1be84c8