Add config to send SMS on 1x

When UE is attached to eHRPD network, IMS is registered and
there is an active 1xRTT voice call, the config determines
whether to send SMS over 1x. Default value is true

CRs-Fixed: 565247

Conflicts:
core/res/res/values/symbols.xml
Change-Id: Ie4e00eb57ef439e9383c616cd1b60108bcfd505f