[MTD] Initialize 'writesize'

Signed-off-by: Artem B. Bityutskiy <dedekind@infradead.org>
diff --git a/drivers/mtd/devices/block2mtd.c b/drivers/mtd/devices/block2mtd.c
index 0d98c22..be3f1c1 100644
--- a/drivers/mtd/devices/block2mtd.c
+++ b/drivers/mtd/devices/block2mtd.c
@@ -324,6 +324,7 @@
 
 	dev->mtd.size = dev->blkdev->bd_inode->i_size & PAGE_MASK;
 	dev->mtd.erasesize = erase_size;
+	dev->mtd.writesize = 1;
 	dev->mtd.type = MTD_RAM;
 	dev->mtd.flags = MTD_CAP_RAM;
 	dev->mtd.erase = block2mtd_erase;