telephony: disable the use of SMS_EXPECT_MORE by default (1/2)

CodeAurora added the use of the RIL_REQUEST_SEND_SMS_EXPECT_MORE API
which is not supported by every RIL. Disabled it by default to reflect
AOSP behavior and added a flag to enable it.

Change-Id: I837c161bbca3960e7458ea049f896218d5e60a63