iommu/fsl_pamu: remove support for multiple windows

iommu/fsl_pamu: remove support for multiple windows

The only domains allocated forces use of a single window.  Remove all
the code related to multiple window support, as well as the need for
qman_portal to force a single window.

Remove the now unused DOMAIN_ATTR_WINDOWS iommu_attr.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Will Deacon <will@kernel.org>
Acked-by: Li Yang <leoyang.li@nxp.com>
Link: https://lore.kernel.org/r/20210401155256.298656-6-hch@lst.de
Signed-off-by: Joerg Roedel <jroedel@suse.de>