namehint: Don't enumerate as duplex if only a single direction is defined
namehint: Don't enumerate as duplex if only a single direction is defined

When a hint description has only either device_input or device_output,
we shouldn't handle it as a full duplex but rather a single
direction.  In that way, we can avoid to list up a playback stream
like dmix or surround51 as a capture stream in the namehint.

Reported-by: Trent Reed <0b8fd97b81c25c229d8d5fc291d15618f2bfd1b5@gmail.com>
Signed-off-by: Takashi Iwai <4596b3305151c7ee743192a95d394341e3d3b644@suse.de>

zedongchen/alsa-lib,tiwai/alsa-lib,zedongchen/alsa-lib,takaswie/alsa-lib,tiwai/alsa-lib,alsa-project/alsa-lib,zedongchen/alsa-lib,takaswie/alsa-lib,takaswie/alsa-lib,zedongchen/alsa-lib,alsa-project/alsa-lib,alsa-project/alsa-lib,takaswie/alsa-lib,tiwai/alsa-lib,tiwai/alsa-lib,zedongchen/alsa-lib,takaswie/alsa-lib,alsa-project/alsa-lib