iommu/sprd: Add missing force_aperture

force_aperture was intended to false only by GART drivers that have an
identity translation outside the aperture. This does not describe sprd, so
add the missing 'force_aperture = true'.

Fixes: b23e4fc4 ("iommu: add Unisoc IOMMU basic driver")
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Acked-by: Chunyan Zhang <zhang.lyra@gmail.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>