iommu/dma: Move PCI window region reservation back into dma specific path.

This pretty much reverts commit 273df963 ("iommu/dma: Make PCI
window reservation generic")  by moving the PCI window region
reservation back into the dma specific path so that these regions
doesn't get exposed via the IOMMU API interface. With this change,
the vfio interface will report only iommu specific reserved regions
to the user space.

Cc: Joerg Roedel <joro@8bytes.org>
Signed-off-by: Shameer Kolothum <shameerali.kolothum.thodi@huawei.com>
Reviewed-by: Robin Murphy <robin.murphy@arm.com>
Fixes: 273df963 ('iommu/dma: Make PCI window reservation generic')
Signed-off-by: Joerg Roedel <jroedel@suse.de>