Update to v4.17.3 kernel headers.

Test: Builds, boots on a walleye.
Change-Id: I389d8b61ec00ea309e38d1b1a2e0dace48c21edb
diff --git a/libc/kernel/uapi/linux/uvcvideo.h b/libc/kernel/uapi/linux/uvcvideo.h
index 5d832d4..7ae7aad 100644
--- a/libc/kernel/uapi/linux/uvcvideo.h
+++ b/libc/kernel/uapi/linux/uvcvideo.h
@@ -61,4 +61,11 @@
 };
 #define UVCIOC_CTRL_MAP _IOWR('u', 0x20, struct uvc_xu_control_mapping)
 #define UVCIOC_CTRL_QUERY _IOWR('u', 0x21, struct uvc_xu_control_query)
+struct uvc_meta_buf {
+  __u64 ns;
+  __u16 sof;
+  __u8 length;
+  __u8 flags;
+  __u8 buf[];
+} __packed;
 #endif