audio-hal: select right input device while enable fluence

regular0 device(a source device, defined in pulseaudio
conf file) using 2 channels, will not use right device
while enabled fluence, because limited to 1 channels in
function 'platform_get_input_snd_device' of platform.c

Change-Id: I584ae06329b7881344620af2468f8b0004412dbd