hal: Set sampling rate for stream_out

Propagate sampling rate to platform_get_output_snd_device to
properly detect 44.1 kHz usecases. Also remove usage of
audio_devices_t in platform_set_echo reference as it does not
contain the sampling rate necessary for
platform_get_output_snd_device. Check device ref counts instead.

CRs-Fixed: 955740
Change-Id: Iaeb53fb362852416603cd57ba15da37b30973c0f