ALSA: echoaudio: More constification

Apply const prefix to the static channel list table.

Just for minor optimization and no functional changes.

Link: https://lore.kernel.org/r/20200105144823.29547-63-tiwai@suse.deSigned-off-by: Takashi Iwai <tiwai@suse.de>

sound/pci/echoaudio/echoaudio.c

@@ -23,7 +23,7 @@ MODULE_PARM_DESC(id, "ID string for " ECHOCARD_NAME " soundcard.");
 module_param_array(enable, bool, NULL, 0444);
 MODULE_PARM_DESC(enable, "Enable " ECHOCARD_NAME " soundcard.");
 
-static unsigned int channels_list[10] = {1, 2, 4, 6, 8, 10, 12, 14, 16, 999999};
+static const unsigned int channels_list[10] = {1, 2, 4, 6, 8, 10, 12, 14, 16, 999999};
 static const DECLARE_TLV_DB_SCALE(db_scale_output_gain, -12800, 100, 1);