ALSA: scarlett2: Fix Mute/Dim/MSD Mode control names

Append "Playback Switch" to the names of "Mute" and "Dim" controls,
and append "Switch" to the "MSD Mode" control as per
Documentation/sound/designs/control-names.rst.
Signed-off-by: Geoffrey D. Bennett <g@b4.vu>
Link: https://lore.kernel.org/r/77f1000652c37e3217fb8dad8e156bc6392abc0b.1626959758.git.g@b4.vuSigned-off-by: Takashi Iwai <tiwai@suse.de>

sound/usb/mixer_scarlett_gen2.c

@@ -228,7 +228,7 @@ enum {
 };
 
 static const char *const scarlett2_dim_mute_names[SCARLETT2_DIM_MUTE_COUNT] = {
-	"Mute", "Dim"
+	"Mute Playback Switch", "Dim Playback Switch"
 };
 
 /* Description of each hardware port type:
@@ -3455,7 +3455,7 @@ static int scarlett2_add_msd_ctl(struct usb_mixer_interface *mixer)
 
 	/* Add MSD control */
 	return scarlett2_add_new_ctl(mixer, &scarlett2_msd_ctl,
-				     0, 1, "MSD Mode", NULL);
+				     0, 1, "MSD Mode Switch", NULL);
 }
 
 /*** Cleanup/Suspend Callbacks ***/