ALSA: HDA: Fix stream assignment for host in decoupled mode

This fixes issue in assigning host stream in case of
decoupled mode. The check to verify if the stream is already
in use was wrong so fix that

Signed-off-by: Jeeja KP <jeeja.kp@intel.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>