usb: dwc3-msm: Add support for IOMMU

On platforms where an IOMMU is used, create a mapping and attach
the platform device to it. This will allow DMA translations through
the IOMMU.

This mapping requires setting the DOMAIN_ATTR_ATOMIC flag, as USB
tends to call DMA map/unmap operations in interrupt context. Due to
the additional clock/regulator resource requirements this imposes,
we should not leave the MMU attached when USB is not in use. Hence
perform the MMU attach/detach operation in conjunction with the
resume/suspend functions when the cable is connected/removed.

Change-Id: I98326ba4ffacbf203969037ffa994ec825d74c78
Signed-off-by: Jack Pham <jackp@codeaurora.org>