soc/intel/fsp_broadwell_de: Add fixed VT-d MMIO range to the resources

soc/intel/fsp_broadwell_de: Add fixed VT-d MMIO range to the resources

FSP initializes the VT-d feature on Broadwell-DE and assigns an address
space to the MMIO range. coreboot's resource allocator needs to be aware
of this fixed resource as otherwise the address can be assigned to a
different PCI device. In this case addresses are overlapped and the VT-d
range is not accessible any more.

To deal with it the right way add a fixed MMIO resource to the resources
list if VT-d BAR is enabled.

TEST=Booted into Linux and checked coreboot log for resource assignment.

Change-Id: I626ac17420eadc0b49031e850f0f40b3b221a098
Signed-off-by: Werner Zeh <werner.zeh@siemens.com>
Reviewed-on: https://review.coreboot.org/28672
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Nico Huber <nico.h@gmx.de>
Reviewed-by: Philipp Deppenwiese <zaolin.daisuki@gmail.com>