xen/arm: smmuv1: Set privileged attr to 'default'

xen/arm: smmuv1: Set privileged attr to 'default'

Backport commit e19898077cfb642fe151ba22981e795c74d9e114
"iommu/arm-smmu: Set privileged attribute to 'default' instead of
'unprivileged'"

Original commit message:
    Currently the driver sets all the device transactions privileges
    to UNPRIVILEGED, but there are cases where the iommu masters wants
    to isolate privileged supervisor and unprivileged user.
    So don't override the privileged setting to unprivileged, instead
    set it to default as incoming and let it be controlled by the
    pagetable settings.

    Acked-by: Will Deacon <will.deacon@arm.com>
    Signed-off-by: Sricharan R <sricharan@codeaurora.org>
    Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Rahul Singh <rahul.singh@arm.com>
Acked-by: Stefano Stabellini <sstabellini@kernel.org>
Tested-by: Stefano Stabellini <sstabellini@kernel.org>