virtio/vsock: add 'VIRTIO_VSOCK_SEQ_EOR' bit.

This bit is used to handle POSIX MSG_EOR flag passed from
userspace in 'send*()' system calls. It marks end of each
record and is visible to receiver using 'recvmsg()' system
call.
Signed-off-by: Arseny Krasnov <arseny.krasnov@kaspersky.com>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Link: https://lore.kernel.org/r/20210903123225.3273425-1-arseny.krasnov@kaspersky.comSigned-off-by: Michael S. Tsirkin <mst@redhat.com>

include/uapi/linux/virtio_vsock.h

@@ -98,6 +98,7 @@ enum virtio_vsock_shutdown {
 /* VIRTIO_VSOCK_OP_RW flags values */
 enum virtio_vsock_rw {
 	VIRTIO_VSOCK_SEQ_EOM = 1,
+	VIRTIO_VSOCK_SEQ_EOR = 2,
 };
 
 #endif /* _UAPI_LINUX_VIRTIO_VSOCK_H */