mtd_dataflash: unbreak erase support

Commit 5b7f3a50 (fix dataflash 64-bit divisions) unfortunately
introduced a typo. Erase addr and len were swapped in the pageaddr
calculation, causing the wrong sectors to get erased.
Signed-off-by: NPeter Korsgaard <jacmet@sunsite.dk>
Acked-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>
Signed-off-by: NDavid Woodhouse <David.Woodhouse@intel.com>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

drivers/mtd/devices/mtd_dataflash.c

@@ -178,7 +178,7 @@ static int dataflash_erase(struct mtd_info *mtd, struct erase_info *instr)
 		/* Calculate flash page address; use block erase (for speed) if
 		 * we're at a block boundary and need to erase the whole block.
 		 */
-		pageaddr = div_u64(instr->len, priv->page_size);
+		pageaddr = div_u64(instr->addr, priv->page_size);
 		do_block = (pageaddr & 0x7) == 0 && instr->len >= blocksize;
 		pageaddr = pageaddr << priv->page_offset;