MdeModulePkg/PciHostBridge: Don't assume resources are fully NonExistent

MdeModulePkg/PciHostBridge: Don't assume resources are fully NonExistent

The patch removes the assumption that the resources claimed by root
bridges should not exist. Because resources might have been added:
1. by platform modules either in PEI through resource HOB, or in DXE,
   before the PCI host bridge driver runs.
2. Resources claimed by different root bridges may overlap so that
   resource adding operation for latter root bridges may fail if
   we assume the resource should not exist.

In real world, this patch is to fit OVMF platform needs because
different root bridges in OVMF platform shares the same resources.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Ruiyu Ni <ruiyu.ni@intel.com>
[lersek@redhat.com: intersection-based implementation]
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Cc: Ruiyu Ni <ruiyu.ni@intel.com>
Reviewed-by: Ruiyu Ni <ruiyu.ni@intel.com>