ARM: dma-mapping: use PMD size for section unmap

The dma_contiguous_remap() function clears existing section maps using
the wrong size (PGDIR_SIZE instead of PMD_SIZE).  This is a bug which
does not affect non-LPAE systems, where PGDIR_SIZE and PMD_SIZE are the same.
On LPAE systems, however, this bug causes the kernel to hang at this point.

This fix has been tested on both LPAE and non-LPAE kernel builds.
Signed-off-by: NVitaly Andrianov <vitalya@ti.com>
Signed-off-by: NMarek Szyprowski <m.szyprowski@samsung.com>

arch/arm/mm/dma-mapping.c

@@ -295,7 +295,7 @@ void __init dma_contiguous_remap(void)
 		 * Clear previous low-memory mapping
 		 */
 		for (addr = __phys_to_virt(start); addr < __phys_to_virt(end);
-		     addr += PGDIR_SIZE)
+		     addr += PMD_SIZE)
 			pmd_clear(pmd_off_k(addr));
 
 		iotable_init(&map, 1);