[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/nand/nandsim.c b/drivers/mtd/nand/nandsim.c
index 6903f5b9..8674f1e 100644
--- a/drivers/mtd/nand/nandsim.c
+++ b/drivers/mtd/nand/nandsim.c
@@ -369,7 +369,7 @@
 	/* Initialize the NAND flash parameters */
 	ns->busw = chip->options & NAND_BUSWIDTH_16 ? 16 : 8;
 	ns->geom.totsz    = mtd->size;
-	ns->geom.pgsz     = mtd->oobblock;
+	ns->geom.pgsz     = mtd->writesize;
 	ns->geom.oobsz    = mtd->oobsize;
 	ns->geom.secsz    = mtd->erasesize;
 	ns->geom.pgszoob  = ns->geom.pgsz + ns->geom.oobsz;