ALSA: FCP: Add Focusrite ISA C8X support

Add USB PID 0x821e to the list of devices handled by the Focusrite
Control Protocol (FCP) driver.

Cc: stable@vger.kernel.org
Signed-off-by: Geoffrey D. Bennett <g@b4.vu>
Link: https://patch.msgid.link/ajlw4HK+2RSW3nUl@m.b4.vu
Signed-off-by: Takashi Iwai <tiwai@suse.de>

Author: geoffreybennett

sound/usb/mixer_quirks.c

@@ -4526,6 +4526,7 @@ int snd_usb_mixer_apply_create_quirk(struct usb_mixer_interface *mixer)
 	case USB_ID(0x1235, 0x821b): /* Focusrite Scarlett 16i16 4th Gen */
 	case USB_ID(0x1235, 0x821c): /* Focusrite Scarlett 18i16 4th Gen */
 	case USB_ID(0x1235, 0x821d): /* Focusrite Scarlett 18i20 4th Gen */
+	case USB_ID(0x1235, 0x821e): /* Focusrite ISA C8X */
 		err = snd_fcp_init(mixer);
 		break;