sw64: iommu: work around iova mapping on pci bars

Sunway inclusion
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I5G5T3



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Since the RCs of SW64 chipset do not support Peer-to-Peer DMA, we used
to return -EINVAL error on iova mampping on PCI BARs. However, it will
cause driver loading errors when QEMU calls vfio module to passthrough
PCI devices with this kind of BARs, shown as follows:
> qemu-system-sw64: VFIO_MAP_DMA: -22
> qemu-system-sw64: vfio_dma_map(0x121c28020, 0x8800c0000000, 0x40000,
  0x4165f21b2000) = -22 (Invalid argument)
> qemu: hardware error: vfio: DMA mapping failed, unable to continue

To fix this problem, this patch will return success on the iova mapping
of PCI BARs that pretends to support this feature.

Signed-off-by: Zhou Qihang <zhouqihang@wxiat.com>

Signed-off-by: Gu Zitao <guzitao@wxiat.com>