hal: Fix EC not working with some VoIP app

Echo reference must be before starting input stream. But in
some cases, input stream is started first and then the output
stream. As the primary output is not started, echo reference is
set based on AUDIO_DEVICE_NONE.

Fix by using primary output's device even if it is in standby.

Bug: 23720819
Change-Id: I1cf2b93ea52219489964e09ee671ef008e81255c