[MTD] Fix module refcounting in NAND board drivers.

The _board_ driver needs to be mtd->owner, and it in turn pins the
nand.ko module. Fix them all to actually do that, and fix nand.ko not to
overwrite it -- and also to check that the caller sets it, if the caller
is a module.

Signed-off-by: David Woodhouse <dwmw2@infradead.org>
diff --git a/drivers/mtd/nand/nandsim.c b/drivers/mtd/nand/nandsim.c
index a0af92c..6903f5b 100644
--- a/drivers/mtd/nand/nandsim.c
+++ b/drivers/mtd/nand/nandsim.c
@@ -1546,6 +1546,8 @@
 		chip->options |= NAND_BUSWIDTH_16;
 	}
 
+	nsmtd->owner = THIS_MODULE;
+
 	if ((retval = nand_scan(nsmtd, 1)) != 0) {
 		NS_ERR("can't register NAND Simulator\n");
 		if (retval > 0)