ARM: dts: msm: Enable iommu's atomic attribute for SD card

Set the SD card's iommu "atomic" attribute. The SD card driver
may acquire a spinlock before calling the iommu's unmap.
Setting the SD card driver's iommu attribute to "atomic" to ensure
the iommu driver doesn't invoke functions that might sleep
in the SD card driver's path.

Change-Id: I215498e8994a56fe1e4e46ea393afff1e81e66c5