nixos/alsa: disable OSSEmulation by default

OSS Emulation is considered incomplete so disabling it by default.
Using user level alsa-oss library (nix-env -iA nixos.alsaOss) over
this kernel module is recommended.

nixos/doc/manual/release-notes/rl-2103.xml

@@ -461,6 +461,11 @@ self: super:
       mouse section.
      </para>
    </listitem>
+   <listitem>
+    <para>
+     ALSA OSS emulation (<varname>sound.enableOSSEmulation</varname>) is now disabled by default.
+    </para>
+   </listitem>
   </itemizedlist>
  </section>
 

nixos/modules/services/audio/alsa.nix

@@ -32,7 +32,7 @@ in
 
       enableOSSEmulation = mkOption {
         type = types.bool;
-        default = true;
+        default = false;
         description = ''
           Whether to enable ALSA OSS emulation (with certain cards sound mixing may not work!).
         '';