OvmfPkg/PciHostBridgeUtilityLib: Extend GetRootBridges() with BusMin/BusMax

OvmfPkg/PciHostBridgeUtilityLib: Extend GetRootBridges() with BusMin/BusMax

Extend parameter list of PciHostBridgeUtilityGetRootBridges() with BusMin/
BusMax, so that the utility function could be compatible with ArmVirtPkg
who uses mutable bus range [BusMin, BusMax] insteand of [0, PCI_MAX_BUS].

BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=3059

Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Ard Biesheuvel <ard.biesheuvel@arm.com>
Signed-off-by: Jiahui Cen <cenjiahui@huawei.com>
Message-Id: <20210119011302.10908-10-cenjiahui@huawei.com>
[lersek@redhat.com: fix logging of UINTN values BusMin, BusMax]
[lersek@redhat.com: keep zeroing of (*Count) centralized]
[lersek@redhat.com: fix typos in ExtraRootBridges comment]
Reviewed-by: Laszlo Ersek <lersek@redhat.com>