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/drivers/char/nvram.c b/drivers/char/nvram.c
index 678fa97..25264d6 100644
--- a/drivers/char/nvram.c
+++ b/drivers/char/nvram.c
@@ -389,22 +389,9 @@ static int nvram_proc_read(struct seq_file *seq, void *offset)
 	return 0;
 }
 
-static int nvram_proc_open(struct inode *inode, struct file *file)
-{
-	return single_open(file, nvram_proc_read, NULL);
-}
-
-static const struct file_operations nvram_proc_fops = {
-	.owner		= THIS_MODULE,
-	.open		= nvram_proc_open,
-	.read		= seq_read,
-	.llseek		= seq_lseek,
-	.release	= single_release,
-};
-
 static int nvram_add_proc_fs(void)
 {
-	if (!proc_create("driver/nvram", 0, NULL, &nvram_proc_fops))
+	if (!proc_create_single("driver/nvram", 0, NULL, nvram_proc_read))
 		return -ENOMEM;
 	return 0;
 }