osxaudiosink: Only fix up channels/layout for PCM caps while probing
osxaudiosink: Only fix up channels/layout for PCM caps while probing

It's unlikely that setting a channel layout will do much for AC3/DTS
streams. If we find at some point that it does make sense, we can
perform the structure copying unconditionally (i.e., the current code is
wrong, since AC3/DTS will get two structures now - one with the channel
layout, one without).

https://bugzilla.gnome.org/show_bug.cgi?id=740987

stfl/gst-plugins-good,shelsonjava/gst-plugins-good,StreamUtils/gst-plugins-good,hizukiayaka/gst-plugins-good,GStreamer/gst-plugins-good,pexip/gst-plugins-good,sh0/gst-plugins-good,veo-labs/gst-plugins-good,vatavuserban/gst-plugins-good,freedesktop-unofficial-mirror/gstreamer__gst-plugins-good,StreamUtils/gst-plugins-good,Kurento/gst-plugins-good,freedesktop-unofficial-mirror/gstreamer__gst-plugins-good,ijsf/OpenWebRTC-gst-plugins-good,veo-labs/gst-plugins-good,BigBrother-International/gst-plugins-good,sebras/gst-plugins-good,ikonst/gst-plugins-good,sh0/gst-plugins-good,Kurento/gst-plugins-good,veo-labs/gst-plugins-good,GrokImageCompression/gst-plugins-good,vatavuserban/gst-plugins-good,chamois94/gst-plugins-good,veo-labs/gst-plugins-good,kittee/gst-plugins-good,loshca/gst-plugins-good,GStreamer/gst-plugins-good,froggatt/gst-plugins-good-m,vatavuserban/gst-plugins-good,chamois94/gst-plugins-good,sebras/gst-plugins-good,chamois94/gst-plugins-good,shelsonjava/gst-plugins-good,ijsf/OpenWebRTC-gst-plugins-good,freedesktop-unofficial-mirror/gstreamer__gst-plugins-good,hizukiayaka/gst-plugins-good,pexip/gst-plugins-good,loshca/gst-plugins-good,kittee/gst-plugins-good,froggatt/gst-plugins-good-m,GStreamer/gst-plugins-good,shelsonjava/gst-plugins-good,ikonst/gst-plugins-good,froggatt/gst-plugins-good-m,BigBrother-International/gst-plugins-good,StreamUtils/gst-plugins-good,GrokImageCompression/gst-plugins-good,Kurento/gst-plugins-good,ikonst/gst-plugins-good,stfl/gst-plugins-good,rawoul/gst-plugins-good,pexip/gst-plugins-good,ijsf/OpenWebRTC-gst-plugins-good,loshca/gst-plugins-good,pexip/gst-plugins-good,kittee/gst-plugins-good,sebras/gst-plugins-good,chamois94/gst-plugins-good,freedesktop-unofficial-mirror/gstreamer__gst-plugins-good,rawoul/gst-plugins-good,sh0/gst-plugins-good,sh0/gst-plugins-good,Kurento/gst-plugins-good,BigBrother-International/gst-plugins-good,hizukiayaka/gst-plugins-good,loshca/gst-plugins-good,ijsf/OpenWebRTC-gst-plugins-good,hizukiayaka/gst-plugins-good,GrokImageCompression/gst-plugins-good,kittee/gst-plugins-good,BigBrother-International/gst-plugins-good,GStreamer/gst-plugins-good,shelsonjava/gst-plugins-good,sebras/gst-plugins-good,pexip/gst-plugins-good,rawoul/gst-plugins-good,Kurento/gst-plugins-good,vatavuserban/gst-plugins-good,froggatt/gst-plugins-good-m,GrokImageCompression/gst-plugins-good,stfl/gst-plugins-good,rawoul/gst-plugins-good,StreamUtils/gst-plugins-good,stfl/gst-plugins-good,ikonst/gst-plugins-good