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>

fs/fscache/proc.c

@@ -26,8 +26,8 @@ int __init fscache_proc_init(void)
 		goto error_dir;
 
 #ifdef CONFIG_FSCACHE_STATS
-	if (!proc_create("fs/fscache/stats", S_IFREG | 0444, NULL,
-			 &fscache_stats_fops))
+	if (!proc_create_single("fs/fscache/stats", S_IFREG | 0444, NULL,
+			fscache_stats_show))
 		goto error_stats;
 #endif