gpu: ion: Move MFC heap to different address

Video hardware has the following requirements for
ION heaps:

1. MM heap must be at a higher address than FW heap.
2. MFC heap must at a higher address than FW
3. MM heap must be adjacent to FW heap.
   (There cannot be another heap between FW and MM heap)
4. MM and MFC heap cannot be more than 256MB away
   from the base address of the FW heap.

MM heap is configured as a reusable heap (FMEM heap) and FMEM
is carved out at a much higher address than the other heaps breaking
the above requirements. To support the above requirements the
MFC heap together with the FW heap must be carved out at the same
location as MM heap.

Change-Id: Ie0acb4b267d4307190ea3cd9ff23c710ffa1a538
Signed-off-by: Olav Haugan <ohaugan@codeaurora.org>