iommu/arm-smmu: Wire up map_sg for arm-smmu-v3

iommu/arm-smmu: Wire up map_sg for arm-smmu-v3

BugLink: http://bugs.launchpad.net/bugs/1607404
commit 9aeb26cfc2abc96be42b9df2d0f2dc5d805084ff upstream.

The map_sg callback is missing from arm_smmu_ops, but is required by
iommu.h. Similarly to most other IOMMU drivers, connect it to
default_iommu_map_sg.

Signed-off-by: Jean-Philippe Brucker <jean-philippe.brucker@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>