alsa: add enumeration of iec958 format

For hdmi and iec958 devices, enumerate the iec958 formats and
codecs. Initially only PCM is supported as a codec but with
a property or an init option, the list of codecs can be dynamically
configured.

src/daemon/media-session.d/alsa-monitor.conf

@@ -111,6 +111,7 @@ rules = [
                 #api.alsa.disable-mmap  = false
                 #api.alsa.disable-batch = false
                 #api.alsa.use-chmap     = false
+                #iec958.codecs          = [ PCM DTS AC3 MPEG MPEG2-AAC EAC3 TrueHD DTS-HD ]
             }
         }
     }