mtd: omap2: fix resource leak in prefetch-busy path

If prefetch engine is busy, current code "forgets" to call
dma_unmap_single(), which results in a deadlock later, so add it.
Signed-off-by: Grazvydas Ignotas <notasas@gmail.com>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>

drivers/mtd/nand/omap2.c

@@ -402,7 +402,7 @@ static inline int omap_nand_dma_transfer(struct mtd_info *mtd, void *addr,
 			PREFETCH_FIFOTHRESHOLD_MAX, 0x1, len, is_write);
 	if (ret)
 		/* PFPW engine is busy, use cpu copy method */
-		goto out_copy;
+		goto out_copy_unmap;
 
 	init_completion(&info->comp);
 
@@ -421,6 +421,8 @@ static inline int omap_nand_dma_transfer(struct mtd_info *mtd, void *addr,
 	dma_unmap_single(&info->pdev->dev, dma_addr, len, dir);
 	return 0;
 
+out_copy_unmap:
+	dma_unmap_single(&info->pdev->dev, dma_addr, len, dir);
 out_copy:
 	if (info->nand.options & NAND_BUSWIDTH_16)
 		is_write == 0 ? omap_read_buf16(mtd, (u_char *) addr, len)