[MTD] Introduce writesize

At least two flashes exists that have the concept of a minimum write unit,
similar to NAND pages, but no other NAND characteristics.  Therefore, rename
the minimum write unit to "writesize" for all flashes, including NAND.

Signed-off-by: Joern Engel <joern@wh.fh-wedel.de>
diff --git a/drivers/mtd/mtdpart.c b/drivers/mtd/mtdpart.c
index 29ed5ab..082662f 100644
--- a/drivers/mtd/mtdpart.c
+++ b/drivers/mtd/mtdpart.c
@@ -398,7 +398,7 @@
 		slave->mtd.type = master->type;
 		slave->mtd.flags = master->flags & ~parts[i].mask_flags;
 		slave->mtd.size = parts[i].size;
-		slave->mtd.oobblock = master->oobblock;
+		slave->mtd.writesize = master->writesize;
 		slave->mtd.oobsize = master->oobsize;
 		slave->mtd.oobavail = master->oobavail;
 		slave->mtd.ecctype = master->ecctype;