mtd: Fix handling of mtdname in txx9ndfmc.c

As pointed out by Kay Sievers, the name size limit is gone
from the driver-core, and BUS_ID_SIZE is obsolescent.

Rather than just papering over the problem by replacing the mtdname
array size with an arbitrary '20 + 2', fix the problem properly and
handle arbitrary name sizes.
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>

drivers/mtd/nand/txx9ndfmc.c

@@ -64,7 +64,7 @@ struct txx9ndfmc_priv {
 	struct nand_chip chip;
 	struct mtd_info mtd;
 	int cs;
-	char mtdname[BUS_ID_SIZE + 2];
+	const char *mtdname;
 };
 
 #define MAX_TXX9NDFMC_DEV	4
@@ -334,11 +334,17 @@ static int __init txx9ndfmc_probe(struct platform_device *dev)
 
 		if (plat->ch_mask != 1) {
 			txx9_priv->cs = i;
-			sprintf(txx9_priv->mtdname, "%s.%u",
+			txx9_priv->mtdname = kasprintf(GFP_KERNEL, "%s.%u",
 						       dev_name(&dev->dev), i);
+			if (!txx9_priv->mtdname) {
+				kfree(txx9_priv);
+				dev_err(&dev->dev,
+					"Unable to allocate TXx9 NDFMC MTD device name.\n");
+				continue;
+			}
 		} else {
 			txx9_priv->cs = -1;
-			strcpy(txx9_priv->mtdname, dev_name(&dev->dev));
+			txx9_priv->mtdname = dev_name(&dev->dev);
 		}
 		if (plat->wide_mask & (1 << i))
 			chip->options |= NAND_BUSWIDTH_16;
@@ -385,6 +391,8 @@ static int __exit txx9ndfmc_remove(struct platform_device *dev)
 		kfree(drvdata->parts[i]);
 #endif
 		del_mtd_device(mtd);
+		if (txx9_priv->mtdname != dev_name(&dev->dev))
+			kfree(txx9_priv->mtdname);
 		kfree(txx9_priv);
 	}
 	return 0;