[MTD] assume mtd->writesize is 1 for NOR flashes

Signed-off-by: Artem B. Bityitskiy
diff --git a/drivers/mtd/chips/amd_flash.c b/drivers/mtd/chips/amd_flash.c
index 9e46650..16eaca6 100644
--- a/drivers/mtd/chips/amd_flash.c
+++ b/drivers/mtd/chips/amd_flash.c
@@ -730,6 +730,7 @@
 		offset += dev_size;
 	}
 	mtd->type = MTD_NORFLASH;
+	mtd->writesize = 1;
 	mtd->flags = MTD_CAP_NORFLASH;
 	mtd->name = map->name;
 	mtd->erase = amd_flash_erase;