OvmfPkg/VirtioFsDxe: implement the wrapper function for FUSE_FORGET
    
    Add the VirtioFsFuseForget() function, for sending the FUSE_FORGET command
    to the Virtio Filesystem device.
    
    This is an unusual command in that it doesn't generate any response from
    the FUSE server.
    
    Cc: Ard Biesheuvel <ard.biesheuvel@arm.com>
    Cc: Jordan Justen <jordan.l.justen@intel.com>
    Cc: Philippe Mathieu-Daudé <philmd@redhat.com>
    Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=3097
    Signed-off-by: Laszlo Ersek <lersek@redhat.com>