Removed snd_config_string_replace function.

Added back modified snd_config_refer_load function.
Added snd_func_private_pcm_subdevice function.
Removed the callback from the snd_sctl_build function (no more required).
Modified alsa.conf to use refer {} blocks again.
Modified card specific conf files to use new snd_func_private_pcm_subdevice function.

src/cards/SI_7018.conf

@@ -58,6 +58,7 @@ pcm.si7018_rear {
 				name "PCM Playback Volume"
 				preserve true
 				lock true
+				index { @func private_pcm_subdevice }
 				value [ 24 24 ]
 			}
 		]