iommu: msm: don't rely on structure format coming from TZ

The format of the secure fault register dump structure in TZ could
change over time. However, it should always adhere to the following
format (each row is 4 bytes wide):

    |-----------|
    | dump_size |
    | reg1_addr |
    | reg1_val  |
    | ...       |
    | regn_addr |
    | regn_val  |
    |-----------|

Rather than relying on the format of the structure, iterate over
the (addr, value) pairs.

Change-Id: I811c7781d6db11ef1eb07c0c1608b8db6978a758
Signed-off-by: Mitchel Humpherys <mitchelh@codeaurora.org>