net: wan: framer: pef2256: Switch to devm_mfd_add_devices()

The driver calls mfd_add_devices() but fails to call mfd_remove_devices()
in error paths after successful MFD device registration and in the remove
function. This leads to resource leaks where MFD child devices are not
properly unregistered.

Replace mfd_add_devices with devm_mfd_add_devices to automatically
manage the device resources.

Fixes: c96e976 ("net: wan: framer: Add support for the Lantiq PEF2256 framer")
Suggested-by: Herve Codina <herve.codina@bootlin.com>
Signed-off-by: Haotian Zhang <vulab@iscas.ac.cn>
Acked-by: Herve Codina <herve.codina@bootlin.com>
Link: https://patch.msgid.link/20251105034716.662-1-vulab@iscas.ac.cn
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: ISCAS-Vulab

drivers/net/wan/framer/pef2256/pef2256.c

@@ -648,7 +648,8 @@ static int pef2256_add_audio_devices(struct pef2256 *pef2256)
 		audio_devs[i].id = i;
 	}
 
-	ret = mfd_add_devices(pef2256->dev, 0, audio_devs, count, NULL, 0, NULL);
+	ret = devm_mfd_add_devices(pef2256->dev, 0, audio_devs, count,
+				   NULL, 0, NULL);
 	kfree(audio_devs);
 	return ret;
 }
@@ -822,8 +823,8 @@ static int pef2256_probe(struct platform_device *pdev)
 
 	platform_set_drvdata(pdev, pef2256);
 
-	ret = mfd_add_devices(pef2256->dev, 0, pef2256_devs,
-			      ARRAY_SIZE(pef2256_devs), NULL, 0, NULL);
+	ret = devm_mfd_add_devices(pef2256->dev, 0, pef2256_devs,
+				   ARRAY_SIZE(pef2256_devs), NULL, 0, NULL);
 	if (ret) {
 		dev_err(pef2256->dev, "add devices failed (%d)\n", ret);
 		return ret;