struct xdp_md_ needs to be renamed to struct xdp_md

[shpalani]

Currently, XDP-for-windows has struct xdp_md_ (with an underscore at the end)

typedef struct **xdp_md_** {
    void *data;               ///< Pointer to start of packet data.
    void *data_end;           ///< Pointer to end of packet data.
    uint64_t data_meta;       ///< Packet metadata.
    uint32_t ingress_ifindex; ///< Ingress interface index.
 
    /* size: 26, cachelines: 1, members: 4 */
    /* last cacheline: 26 bytes */
} xdp_md_t;

As per ebpf, it should be 'struct xdp_md'.