Update to v4.17.3 kernel headers.

Test: Builds, boots on a walleye.
Change-Id: I389d8b61ec00ea309e38d1b1a2e0dace48c21edb
diff --git a/libc/kernel/uapi/linux/usb/audio.h b/libc/kernel/uapi/linux/usb/audio.h
index 121c859..87b8bd5 100644
--- a/libc/kernel/uapi/linux/usb/audio.h
+++ b/libc/kernel/uapi/linux/usb/audio.h
@@ -21,6 +21,7 @@
 #include <linux/types.h>
 #define UAC_VERSION_1 0x00
 #define UAC_VERSION_2 0x20
+#define UAC_VERSION_3 0x30
 #define USB_SUBCLASS_AUDIOCONTROL 0x01
 #define USB_SUBCLASS_AUDIOSTREAMING 0x02
 #define USB_SUBCLASS_MIDISTREAMING 0x03