v3->v4:
* Refactor InitRootBridges/UninitRootBridges/GetRootBridges/FreeRootBridges.
* Fix library dependencies.

v2->v3:
* Rename utility functions under the PciHostBridgeUtilityLib namespace.
* Remove some unused Library dependencies.
* Sort the Include headers.

v1->v2:
* Separated into four patches.
* Factor the same logic parts into a new library.

v3: https://edk2.groups.io/g/devel/message/69382
BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=3059
QEMU: https://lore.kernel.org/qemu-devel/20201119014841.7298-1-cenjiahui@huawei.com/

This patch series adds support for extra pci roots for ARM.

In order to avoid duplicated codes, we introduce a new library
PciHostBridgeUtilityLib which extracts common interfaces from
OvmfPkg/PciHostBridgeLib. It provides conflicts informing and extra pci
roots scanning. Using the utility lib, the uefi could scan for extra
root buses and recognize multiple roots for ARM.

Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Ard Biesheuvel <ard.biesheuvel@arm.com>
Cc: Rebecca Cran <rebecca@bsdio.com>
Cc: Peter Grehan <grehan@freebsd.org>
Cc: Anthony Perard <anthony.perard@citrix.com>
Cc: Julien Grall <julien@xen.org>
Cc: Leif Lindholm <leif@nuviainc.com>
Cc: Sami Mujawar <sami.mujawar@arm.com>
Signed-off-by: Jiahui Cen <cenjiahui@huawei.com>
Signed-off-by: Yubo Miao <miaoyubo@huawei.com>