msm: ion: Do not check for overlapping ion heaps

To support new usecases, HLOS will permit of sharing
of the CMA pool between the ion heaps. Going forward
we do not need to check if the heaps overlap.

Change-Id: I1dee72147fad994a1c88ea9dfcf7402ba98f3609
Signed-off-by: Neeti Desai <neetid@codeaurora.org>