msm: kgsl: Handle a defer from IOMMU

of_dma_configure() will return -EPROBE_DEFER if the IOMMU driver isn't
set up yet. Propagate that error all the way back to probe.

Change-Id: Ic0dedbad3bdda6516386f6eeff485065f83aee9b
Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>