[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/devices/doc2001plus.c b/drivers/mtd/devices/doc2001plus.c
index 0dc5d10..8422c5e 100644
--- a/drivers/mtd/devices/doc2001plus.c
+++ b/drivers/mtd/devices/doc2001plus.c
@@ -483,7 +483,7 @@
 	mtd->size = 0;
 
 	mtd->erasesize = 0;
-	mtd->oobblock = 512;
+	mtd->writesize = 512;
 	mtd->oobsize = 16;
 	mtd->owner = THIS_MODULE;
 	mtd->erase = doc_erase;