OvmfPkg: PciHostBridgeDxe: embed device path in private root bridge struct

OvmfPkg: PciHostBridgeDxe: embed device path in private root bridge struct

Currently we define a device path for each root bridge statically (for all
one of them). Since we'll want to create a dynamic number of root bridges,
replace the static device paths with a common template, embed the actual
device path into the private root bridge structure, and distinguish the
device paths from each other in the UID field (as required by ACPI).

This patch is best viewed with "git show -b".

Cc: Jordan Justen <jordan.l.justen@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Regression-tested-by: Gabriel Somlo <somlo@cmu.edu>
Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>
git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@17957 6f19259b-4bc3-4df7-8a09-765794883524