Update to v4.19 kernel headers.

Test: Builds and boots.
Change-Id: I99a9ed79666e143b47f02ca4e59eed94f69b7e4a
(cherry picked from commit a981e2e52e2e95a65fa9c9b6fb16dcb4c83dd576)
diff --git a/libc/kernel/uapi/linux/vhost.h b/libc/kernel/uapi/linux/vhost.h
index b6c1f9d..e802e02 100644
--- a/libc/kernel/uapi/linux/vhost.h
+++ b/libc/kernel/uapi/linux/vhost.h
@@ -55,6 +55,7 @@
   __u8 type;
 };
 #define VHOST_IOTLB_MSG 0x1
+#define VHOST_IOTLB_MSG_V2 0x2
 struct vhost_msg {
   int type;
   union {
@@ -62,6 +63,14 @@
     __u8 padding[64];
   };
 };
+struct vhost_msg_v2 {
+  __u32 type;
+  __u32 reserved;
+  union {
+    struct vhost_iotlb_msg iotlb;
+    __u8 padding[64];
+  };
+};
 struct vhost_memory_region {
   __u64 guest_phys_addr;
   __u64 memory_size;
@@ -95,6 +104,9 @@
 #define VHOST_SET_VRING_ERR _IOW(VHOST_VIRTIO, 0x22, struct vhost_vring_file)
 #define VHOST_SET_VRING_BUSYLOOP_TIMEOUT _IOW(VHOST_VIRTIO, 0x23, struct vhost_vring_state)
 #define VHOST_GET_VRING_BUSYLOOP_TIMEOUT _IOW(VHOST_VIRTIO, 0x24, struct vhost_vring_state)
+#define VHOST_BACKEND_F_IOTLB_MSG_V2 0x1
+#define VHOST_SET_BACKEND_FEATURES _IOW(VHOST_VIRTIO, 0x25, __u64)
+#define VHOST_GET_BACKEND_FEATURES _IOR(VHOST_VIRTIO, 0x26, __u64)
 #define VHOST_NET_SET_BACKEND _IOW(VHOST_VIRTIO, 0x30, struct vhost_vring_file)
 #define VHOST_F_LOG_ALL 26
 #define VHOST_NET_F_VIRTIO_NET_HDR 27