Skip sending RIL_REQUEST_ALLOW_DATA on single SIM devices

RIL_REQUEST_ALLOW_DATA on single SIM devices causes lab
test cases to fail as it triggers detach on some cases.

There is no need to send this on single SIM devices as the
data subscription is not going to change dynamically.

Test: Telephony data sanity, verified data working upon
      SIM hotswap, preferred network type changes

Bug: 62872229
Bug: 62844965
Change-Id: Ia89e5180b7c023163af176d9ff058375b7765fc2