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/apm-emulation.c b/drivers/char/apm-emulation.c
index a5e2f9e..53436c0 100644
--- a/drivers/char/apm-emulation.c
+++ b/drivers/char/apm-emulation.c
@@ -461,19 +461,6 @@
 
 	return 0;
 }
-
-static int proc_apm_open(struct inode *inode, struct file *file)
-{
-	return single_open(file, proc_apm_show, NULL);
-}
-
-static const struct file_operations apm_proc_fops = {
-	.owner		= THIS_MODULE,
-	.open		= proc_apm_open,
-	.read		= seq_read,
-	.llseek		= seq_lseek,
-	.release	= single_release,
-};
 #endif
 
 static int kapmd(void *arg)
@@ -657,7 +644,7 @@
 	wake_up_process(kapmd_tsk);
 
 #ifdef CONFIG_PROC_FS
-	proc_create("apm", 0, NULL, &apm_proc_fops);
+	proc_create_single("apm", 0, NULL, proc_apm_show);
 #endif
 
 	ret = misc_register(&apm_device);