powerpc: fadump: use lock guard for mutex

use scoped_guard 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/[e-mail]/T/#u

Reviewed-by: Srikar Dronamraju <[e-mail]>
Signed-off-by: Shrikanth Hegde <[e-mail]>
Tested-by: Venkat Rao Bagalkote <[e-mail]>
Reviewed-by: Sourabh Jain <[e-mail]>
Signed-off-by: Madhavan Srinivasan <[e-mail]>
Link: https://patch.msgid.link/[e-mail]

arch/powerpc/kernel/fadump.c

···
 
 static void fadump_invalidate_release_mem(void)
 {
-	mutex_lock(&fadump_mutex);
-	if (!fw_dump.dump_active) {
-		mutex_unlock(&fadump_mutex);
-		return;
+	scoped_guard(mutex, &fadump_mutex) {
+		if (!fw_dump.dump_active)
+			return;
+		fadump_cleanup();
 	}
-
-	fadump_cleanup();
-	mutex_unlock(&fadump_mutex);
 
 	fadump_free_elfcorehdr_buf();
 	fadump_release_memory(fw_dump.boot_mem_top, memblock_end_of_DRAM());