powerpc: eeh: use lock guard for mutex

use guard(mutex) for scope based resource management of mutex.
This would make the code simpler and easier to maintain.

More details on lock guards can be found at
https://lore.kernel.org/all/20230612093537.614161713@infradead.org/T/#u

Reviewed-by: Srikar Dronamraju <srikar@linux.ibm.com>
Signed-off-by: Shrikanth Hegde <sshegde@linux.ibm.com>
Tested-by: Venkat Rao Bagalkote <venkat88@linux.ibm.com>
Signed-off-by: Madhavan Srinivasan <maddy@linux.ibm.com>
Link: https://patch.msgid.link/20250505075333.184463-2-sshegde@linux.ibm.com

Author: Shrikanth Hegde

arch/powerpc/kernel/eeh.c

@@ -1208,16 +1208,16 @@ int eeh_dev_open(struct pci_dev *pdev)
 	struct eeh_dev *edev;
 	int ret = -ENODEV;
 
-	mutex_lock(&eeh_dev_mutex);
+	guard(mutex)(&eeh_dev_mutex);
 
 	/* No PCI device ? */
 	if (!pdev)
-		goto out;
+		return ret;
 
 	/* No EEH device or PE ? */
 	edev = pci_dev_to_eeh_dev(pdev);
 	if (!edev || !edev->pe)
-		goto out;
+		return ret;
 
 	/*
 	 * The PE might have been put into frozen state, but we
@@ -1227,16 +1227,12 @@ int eeh_dev_open(struct pci_dev *pdev)
 	 */
 	ret = eeh_pe_change_owner(edev->pe);
 	if (ret)
-		goto out;
+		return ret;
 
 	/* Increase PE's pass through count */
 	atomic_inc(&edev->pe->pass_dev_cnt);
-	mutex_unlock(&eeh_dev_mutex);
 
 	return 0;
-out:
-	mutex_unlock(&eeh_dev_mutex);
-	return ret;
 }
 EXPORT_SYMBOL_GPL(eeh_dev_open);
 
@@ -1252,22 +1248,20 @@ void eeh_dev_release(struct pci_dev *pdev)
 {
 	struct eeh_dev *edev;
 
-	mutex_lock(&eeh_dev_mutex);
+	guard(mutex)(&eeh_dev_mutex);
 
 	/* No PCI device ? */
 	if (!pdev)
-		goto out;
+		return;
 
 	/* No EEH device ? */
 	edev = pci_dev_to_eeh_dev(pdev);
 	if (!edev || !edev->pe || !eeh_pe_passed(edev->pe))
-		goto out;
+		return;
 
 	/* Decrease PE's pass through count */
 	WARN_ON(atomic_dec_if_positive(&edev->pe->pass_dev_cnt) < 0);
 	eeh_pe_change_owner(edev->pe);
-out:
-	mutex_unlock(&eeh_dev_mutex);
 }
 EXPORT_SYMBOL(eeh_dev_release);