arm/dt: iommu: Remove unnecessary properties

Remove the qcom,iommu-smt-size properties from the device
tree since this information is now read directly out of the
hardware blocks.

Change-Id: I0583b0768c6bb2df803989db590ffd52ceabcafe
Signed-off-by: Stepan Moskovchenko <stepanm@codeaurora.org>