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: I9ae54a3a021cb3513c2b0e8c58b69f3ae118561b
Signed-off-by: Benjamin Gaignard <benjamin.gaignard@linaro.org>
[lauraa: Fix context in ion_priv.h/ion.h and omit Makefile change for now]
Signed-off-by: Laura Abbott <lauraa@codeaurora.org>
diff --git a/include/linux/ion.h b/include/linux/ion.h
index 40d11e2..3a29f20 100644
--- a/include/linux/ion.h
+++ b/include/linux/ion.h
@@ -33,12 +33,14 @@
  * @ION_HEAP_TYPE_CP:	 memory allocated from a prereserved
  *				carveout heap, allocations are physically
  *				contiguous. Used for content protection.
+ * @ION_HEAP_TYPE_DMA:          memory allocated via DMA API
  * @ION_HEAP_END:		helper for iterating over heaps
  */
 enum ion_heap_type {
 	ION_HEAP_TYPE_SYSTEM,
 	ION_HEAP_TYPE_SYSTEM_CONTIG,
 	ION_HEAP_TYPE_CARVEOUT,
+	ION_HEAP_TYPE_DMA,
 	ION_HEAP_TYPE_CUSTOM, /* must be last so device specific heaps always
 				 are at the end of this enum */
 	ION_NUM_HEAPS,
@@ -47,6 +49,7 @@
 #define ION_HEAP_SYSTEM_MASK		(1 << ION_HEAP_TYPE_SYSTEM)
 #define ION_HEAP_SYSTEM_CONTIG_MASK	(1 << ION_HEAP_TYPE_SYSTEM_CONTIG)
 #define ION_HEAP_CARVEOUT_MASK		(1 << ION_HEAP_TYPE_CARVEOUT)
+#define ION_HEAP_TYPE_DMA_MASK         (1 << ION_HEAP_TYPE_DMA)
 
 /**
  * heap flags - the lower 16 bits are used by core ion, the upper 16