mtd: rawnand: marvell: set reg_clk to NULL if it can't be obtained

Don't keep an error-pointer around in the private struct. If this optional
clock can't be obtained, simply set the pointer to NULL instead so we can
use clk_prepare_enable() on it without further checks,

Signed-off-by: Daniel Mack <daniel@zonque.org>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>

drivers/mtd/nand/raw/marvell_nand.c

@@ -2773,17 +2773,19 @@ static int marvell_nfc_probe(struct platform_device *pdev)
 		return ret;
 
 	nfc->reg_clk = devm_clk_get(&pdev->dev, "reg");
-	if (PTR_ERR(nfc->reg_clk) != -ENOENT) {
-		if (!IS_ERR(nfc->reg_clk)) {
-			ret = clk_prepare_enable(nfc->reg_clk);
-			if (ret)
-				goto unprepare_core_clk;
-		} else {
+	if (IS_ERR(nfc->reg_clk)) {
+		if (PTR_ERR(nfc->reg_clk) != -ENOENT) {
 			ret = PTR_ERR(nfc->reg_clk);
 			goto unprepare_core_clk;
 		}
+
+		nfc->reg_clk = NULL;
 	}
 
+	ret = clk_prepare_enable(nfc->reg_clk);
+	if (ret)
+		goto unprepare_core_clk;
+
 	marvell_nfc_disable_int(nfc, NDCR_ALL_INT);
 	marvell_nfc_clear_int(nfc, NDCR_ALL_INT);
 	ret = devm_request_irq(dev, irq, marvell_nfc_isr,
@@ -2864,11 +2866,9 @@ static int __maybe_unused marvell_nfc_resume(struct device *dev)
 	if (ret < 0)
 		return ret;
 
-	if (!IS_ERR(nfc->reg_clk)) {
-		ret = clk_prepare_enable(nfc->reg_clk);
-		if (ret < 0)
-			return ret;
-	}
+	ret = clk_prepare_enable(nfc->reg_clk);
+	if (ret < 0)
+		return ret;
 
 	/*
 	 * Reset nfc->selected_chip so the next command will cause the timing