mtd: rawnand: mtk: fix possible object reference leak

of_find_device_by_node() takes a reference to the struct device
when it finds a match via get_device, there is no need to call
get_device() twice.
We also should make sure to drop the reference to the device
taken by of_find_device_by_node() on driver unbind.

Fixes: 1d6b1e46 ("mtd: mediatek: driver for MTK Smart Device")
Signed-off-by: Wen Yang <yellowriver2010@hotmail.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>

drivers/mtd/nand/raw/mtk_ecc.c

@@ -267,11 +267,15 @@ static struct mtk_ecc *mtk_ecc_get(struct device_node *np)
 	struct mtk_ecc *ecc;
 
 	pdev = of_find_device_by_node(np);
-	if (!pdev || !platform_get_drvdata(pdev))
+	if (!pdev)
 		return ERR_PTR(-EPROBE_DEFER);
 
-	get_device(&pdev->dev);
 	ecc = platform_get_drvdata(pdev);
+	if (!ecc) {
+		put_device(&pdev->dev);
+		return ERR_PTR(-EPROBE_DEFER);
+	}
+
 	clk_prepare_enable(ecc->clk);
 	mtk_ecc_hw_init(ecc);