Update Linux to v5.4.2

Change-Id: Idf6911045d9d382da2cfe01b1edff026404ac8fd
diff --git a/sound/usb/mixer.h b/sound/usb/mixer.h
index 3d12af8..37e1b23 100644
--- a/sound/usb/mixer.h
+++ b/sound/usb/mixer.h
@@ -4,6 +4,8 @@
 
 #include <sound/info.h>
 
+struct media_mixer_ctl;
+
 struct usb_mixer_interface {
 	struct snd_usb_audio *chip;
 	struct usb_host_interface *hostif;
@@ -23,8 +25,13 @@
 	struct urb *rc_urb;
 	struct usb_ctrlrequest *rc_setup_packet;
 	u8 rc_buffer[6];
+	struct media_mixer_ctl *media_mixer_ctl;
 
 	bool disconnected;
+
+	void *private_data;
+	void (*private_free)(struct usb_mixer_interface *mixer);
+	void (*private_suspend)(struct usb_mixer_interface *mixer);
 };
 
 #define MAX_CHANNELS	16	/* max logical channels */