msm: iommu: Correct the size passed to dmac_clean_range()

The size being passed to dmac_clean_range() inside
iommu_map_range is incorrect; instead of providing the
total length of all the chunks in the chunk list, we're
currently passing the length of just one chunk. Fix this
to pass in the right length.

Change-Id: Id9f4ce9be8a21da0e037da987b3e1fbd8d81dd2f
Signed-off-by: Neeti Desai <neetid@codeaurora.org>