Some UEFI systems (observed with a Mac Pro) do not provide
EFI_HII_DATABASE_PROTOCOL. We can continue to function without
providing access to network device settings via HII, so make this
protocol optional and fall back to simply not providing any HII
protocols.
Reported-by: Matt Woodward <pxematt@woodwardcc.com> Tested-by: Matt Woodward <pxematt@woodwardcc.com> Signed-off-by: Michael Brown <mcb30@ipxe.org>