OvmfPkg/VirtioLib: add VirtioMapAllBytesInSharedBuffer() helper function
    
    The function can be used for mapping the system physical address to virtio
    device address using VIRTIO_DEVICE_PROTOCOL.MapSharedBuffer (). The
    function helps with centralizing error handling, and it allows the caller
    to pass in constant or other evaluated expressions for NumberOfBytes.
    
    Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
    Cc: Jordan Justen <jordan.l.justen@intel.com>
    Cc: Tom Lendacky <thomas.lendacky@amd.com>
    Cc: Laszlo Ersek <lersek@redhat.com>
    Contributed-under: TianoCore Contribution Agreement 1.1
    Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
    [lersek@redhat.com: s/This/VirtIo/ in the new function's comment blocks]
    Reviewed-by: Laszlo Ersek <lersek@redhat.com>
    Regression-tested-by: Laszlo Ersek <lersek@redhat.com>