arm64: amd-seattle: Fix PCI bus range due to SMMU limitation

Since PCIe is using SMMUv1 which only supports 15-bit stream ID,
only 7-bit PCI bus id is used to specify stream ID. Therefore,
we only limit the PCI bus range to 0x7f.

Signed-off-by: Suravee Suthikulpanit <Suravee.Suthikulpanit@amd.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>