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/arch/s390/kernel/sysinfo.c b/arch/s390/kernel/sysinfo.c
index fed4960..54f5496 100644
--- a/arch/s390/kernel/sysinfo.c
+++ b/arch/s390/kernel/sysinfo.c
@@ -294,21 +294,9 @@ static int sysinfo_show(struct seq_file *m, void *v)
 	return 0;
 }
 
-static int sysinfo_open(struct inode *inode, struct file *file)
-{
-	return single_open(file, sysinfo_show, NULL);
-}
-
-static const struct file_operations sysinfo_fops = {
-	.open		= sysinfo_open,
-	.read		= seq_read,
-	.llseek		= seq_lseek,
-	.release	= single_release,
-};
-
 static int __init sysinfo_create_proc(void)
 {
-	proc_create("sysinfo", 0444, NULL, &sysinfo_fops);
+	proc_create_single("sysinfo", 0444, NULL, sysinfo_show);
 	return 0;
 }
 device_initcall(sysinfo_create_proc);