msm: kgsl: Clean up IOMMU context bank configuration

Backport the 'new' iommu device structure to all targets
we currently support so that we can have only one device
tree parsing path. Targets using the 'old' iommu driver
don't have an 'iommus' property and instead must lookup
the iommu device by label.

Math is hard, so move it all to the device tree files.
The GPU register region to protect is defined by the
qcom,protect property.  The register offset to use for
GPU context bank progamming is set by the qcom,gpu-offset
property in the "gfx3d_user" device tree node.
Some targets need to use a global 'lock' register to safely
reprogram the context bank registers. This register is not
part of the context bank, so it is specified by the
qcomm,micro-mmu-ctrl property when it is present.

Change-Id: I77036d517218ba1f749b015aa09036eb796baefe
Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>
Signed-off-by: Lynus Vaz <lvaz@codeaurora.org>
Signed-off-by: Carter Cooper <ccooper@codeaurora.org>
Signed-off-by: Jeremy Gebben <jgebben@codeaurora.org>