ARM: dma-mapping: Add maximum alignment order for dma iommu buffers

Alignment order for a dma iommu buffer is set by buffer size. For
large buffer, it is a waste of iommu address space. So configurable
parameter to limit maximum alignment order can reduce the waste.

Signed-off-by: Seung-Woo Kim <sw0312.kim@samsung.com>
Signed-off-by: Kyungmin.park <kyungmin.park@samsung.com>
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>

arch/arm/mm/dma-mapping.c

@@ -1029,6 +1029,9 @@ static inline dma_addr_t __alloc_iova(struct dma_iommu_mapping *mapping,
 	unsigned int count, start;
 	unsigned long flags;
 
+	if (order > CONFIG_ARM_DMA_IOMMU_ALIGNMENT)
+		order = CONFIG_ARM_DMA_IOMMU_ALIGNMENT;
+
 	count = ((PAGE_ALIGN(size) >> PAGE_SHIFT) +
 		 (1 << mapping->order) - 1) >> mapping->order;