gpu: ion: add CMA heap

New heap type ION_HEAP_TYPE_DMA where allocation is done with dma_alloc_coherent API.
device coherent_dma_mask must be set to DMA_BIT_MASK(32).
ion_platform_heap private field is used to retrieve the device linked to CMA,
if NULL the default CMA area is used.
ion_cma_get_sgtable is a copy of dma_common_get_sgtable function which should
be in kernel 3.5

Change-Id: If4b1a3f9c8a6bd72053226208832f4971e44372f
Signed-off-by: Benjamin Gaignard <benjamin.gaignard@linaro.org>
(cherry picked from commit 73260c8acb183c70dd286fa693164438fe7f8e4f)
gpu: ion: Fix performance issue in faulting code

Previously the code to fault ion buffers in one page at a time had a
performance problem caused by the requirement to traverse the sg list
looking for the right page to load in (a result of the fact that the items in
the list may not be of uniform size).  To fix the problem, for buffers
that will be faulted in, also keep a flat array of all the pages in the buffer
to use from the fault handler.  To recover some of the additional memory
footprint this creates per buffer, dirty bits used to indicate which
pages have been faulted in to the cpu are now stored in the low bit of each
page struct pointer in the page array.

Change-Id: I891b077dc0c88ed6d416b256626d8778fd67be84
Signed-off-by: Rebecca Schultz Zavin <rebecca@android.com>
(cherry picked from commit 8b0dfc1b6a6c667f8f14e43840e6f5d1393e4876)