mtd: rawnand: lpc32xx_slc: Switch to using pm_ptr()

The switch to using the gpiod API removed the last user of
lpc32xx_wp_disable() outside #ifdef CONFIG_PM, causing build failures if
CONFIG_PM=n:

    drivers/mtd/nand/raw/lpc32xx_slc.c:318:13: error: ‘lpc32xx_wp_disable’ defined but not used [-Werror=unused-function]
      318 | static void lpc32xx_wp_disable(struct lpc32xx_nand_host *host)
          |             ^~~~~~~~~~~~~~~~~~

Fix this by switching from #ifdef CONFIG_PM to pm_ptr(), increasing
compile-coverage as a side-effect.

Reported-by: noreply@ellerman.id.au
Fixes: 6b923db2 ("mtd: rawnand: lpc32xx_slc: switch to using gpiod API")
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20221027131028.3838303-2-geert@linux-m68k.org

drivers/mtd/nand/raw/lpc32xx_slc.c

@@ -969,7 +969,6 @@ static int lpc32xx_nand_remove(struct platform_device *pdev)
 	return 0;
 }
 
-#ifdef CONFIG_PM
 static int lpc32xx_nand_resume(struct platform_device *pdev)
 {
 	struct lpc32xx_nand_host *host = platform_get_drvdata(pdev);
@@ -1008,11 +1007,6 @@ static int lpc32xx_nand_suspend(struct platform_device *pdev, pm_message_t pm)
 	return 0;
 }
 
-#else
-#define lpc32xx_nand_resume NULL
-#define lpc32xx_nand_suspend NULL
-#endif
-
 static const struct of_device_id lpc32xx_nand_match[] = {
 	{ .compatible = "nxp,lpc3220-slc" },
 	{ /* sentinel */ },
@@ -1022,8 +1016,8 @@ MODULE_DEVICE_TABLE(of, lpc32xx_nand_match);
 static struct platform_driver lpc32xx_nand_driver = {
 	.probe		= lpc32xx_nand_probe,
 	.remove		= lpc32xx_nand_remove,
-	.resume		= lpc32xx_nand_resume,
-	.suspend	= lpc32xx_nand_suspend,
+	.resume		= pm_ptr(lpc32xx_nand_resume),
+	.suspend	= pm_ptr(lpc32xx_nand_suspend),
 	.driver		= {
 		.name	= LPC32XX_MODNAME,
 		.of_match_table = lpc32xx_nand_match,