mmc: mmc_spi: Convert to use for_each_sg()

Use for_each_sg() macro instead of open coded variant.

No functional change intended.
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

drivers/mmc/host/mmc_spi.c

@@ -891,7 +891,7 @@ mmc_spi_data_do(struct mmc_spi_host *host, struct mmc_command *cmd,
 	/* Handle scatterlist segments one at a time, with synch for
 	 * each 512-byte block
 	 */
-	for (sg = data->sg, n_sg = data->sg_len; n_sg; n_sg--, sg++) {
+	for_each_sg(data->sg, sg, data->sg_len, n_sg) {
 		int			status = 0;
 		dma_addr_t		dma_addr = 0;
 		void			*kmap_addr;