regmap: rbtree: convert to DEFINE_SHOW_ATTRIBUTE

Use DEFINE_SHOW_ATTRIBUTE macro to simplify the code.
Signed-off-by: Yangtao Li <tiny.windzz@gmail.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

drivers/base/regmap/regcache-rbtree.c

@@ -177,17 +177,7 @@ static int rbtree_show(struct seq_file *s, void *ignored)
 	return 0;
 }
 
-static int rbtree_open(struct inode *inode, struct file *file)
-{
-	return single_open(file, rbtree_show, inode->i_private);
-}
-
-static const struct file_operations rbtree_fops = {
-	.open		= rbtree_open,
-	.read		= seq_read,
-	.llseek		= seq_lseek,
-	.release	= single_release,
-};
+DEFINE_SHOW_ATTRIBUTE(rbtree);
 
 static void rbtree_debugfs_init(struct regmap *map)
 {