iommu: msm: Only flush the exact list size

Before giving a list of memory chunks to trustzone, the list needs
to be flushed. The list is simply an array of physical addresses.
The current flush routine takes into account the size of the memory
chunk which is incorrect. The memory chunk size is not used in
calculating the list length since the list is a list of pointers.
Adjust the cache flushing routine to flush the actual size of the
list: size of each entry times the number of entries.

Change-Id: I3fbc7cb7e6c823823481b5fb205a1414e76150c9
Signed-off-by: Laura Abbott <lauraa@codeaurora.org>