sf: Minor cleanups.

- Add comments.
- Renamed few macros.
- Add tabs.

Signed-off-by: Jagannadha Sutradharudu Teki <jaganna@xilinx.com>
Signed-off-by: Bo Shen <voice.shen@atmel.com>
diff --git a/drivers/mtd/spi/sf_ops.c b/drivers/mtd/spi/sf_ops.c
index 1003038..dde6231 100644
--- a/drivers/mtd/spi/sf_ops.c
+++ b/drivers/mtd/spi/sf_ops.c
@@ -292,7 +292,7 @@
 			return ret;
 		}
 #endif
-		remain_len = (SPI_FLASH_16MB_BOUN * (bank_sel + 1) - offset);
+		remain_len = (SPI_FLASH_16MB_BOUN * (bank_sel + 1)) - offset;
 		if (len < remain_len)
 			read_len = len;
 		else