Fix failing to send SMS with SMSC over IMS

The encoded SMSC is passed by string, and lower layer expects
hex string, but it cannot be converted from vendor because
of getting bytes from string based on different charset.

To fix it, pass hex string for SMSC over IMS.

Test: Smoke Test
Bug: 120003768

Change-Id: If35709589e7ac303563ab25d4a56a7793d2e0910