proc: introduce proc_create_single{,_data}

Variants of proc_create{,_data} that directly take a seq_file show
callback and drastically reduces the boilerplate code in the callers.

All trivial callers converted over.

Signed-off-by: Christoph Hellwig <hch@lst.de>
diff --git a/fs/proc/softirqs.c b/fs/proc/softirqs.c
index 24072cc..12901dc 100644
--- a/fs/proc/softirqs.c
+++ b/fs/proc/softirqs.c
@@ -25,21 +25,9 @@
 	return 0;
 }
 
-static int softirqs_open(struct inode *inode, struct file *file)
-{
-	return single_open(file, show_softirqs, NULL);
-}
-
-static const struct file_operations proc_softirqs_operations = {
-	.open		= softirqs_open,
-	.read		= seq_read,
-	.llseek		= seq_lseek,
-	.release	= single_release,
-};
-
 static int __init proc_softirqs_init(void)
 {
-	proc_create("softirqs", 0, NULL, &proc_softirqs_operations);
+	proc_create_single("softirqs", 0, NULL, show_softirqs);
 	return 0;
 }
 fs_initcall(proc_softirqs_init);