gpu: ion: Add support for adjacent heaps

ION has to guarantee that two of the heaps are
adjacent to each other. This is due to a limitation
in the hardware. Add code to ensure these heaps
are adjacent.

Change-Id: Icc18437a50e1d872112468d02b61ab47fd70acc9
Signed-off-by: Olav Haugan <ohaugan@codeaurora.org>
[sboyd: drop board file changes]
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>