audio: add -audiodev pa,in|out.latency= to documentation

The "latency" parameter wasn't covered by the documentation.
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: NMarc-André Lureau <marcandre.lureau@redhat.com>
Message-id: 20191004125641.24383-1-stefanha@redhat.com
Signed-off-by: NGerd Hoffmann <kraxel@redhat.com>

qemu-options.hx

@@ -471,6 +471,7 @@ DEF("audiodev", HAS_ARG, QEMU_OPTION_audiodev,
     "-audiodev pa,id=id[,prop[=value][,...]]\n"
     "                server= PulseAudio server address\n"
     "                in|out.name= source/sink device name\n"
+    "                in|out.latency= desired latency in microseconds\n"
 #endif
 #ifdef CONFIG_AUDIO_SDL
     "-audiodev sdl,id=id[,prop[=value][,...]]\n"
@@ -645,6 +646,10 @@ Sets the PulseAudio @var{server} to connect to.
 @item in|out.name=@var{sink}
 Use the specified source/sink for recording/playback.
 
+@item in|out.latency=@var{usecs}
+Desired latency in microseconds.  The PulseAudio server will try to honor this
+value but actual latencies may be lower or higher.
+
 @end table
 
 @item -audiodev sdl,id=@var{id}[,@var{prop}[=@var{value}][,...]]