greybus: Export greybus debugfs folder

Add gb_debugfs_get method to access to gb_debug_root dentry,
in order to use it from other greybus modules.

Signed-off-by: Alexandre Bailon <abailon@baylibre.com>
Signed-off-by: Greg Kroah-Hartman <greg@kroah.com>
diff --git a/drivers/staging/greybus/debugfs.c b/drivers/staging/greybus/debugfs.c
index 770b7c0..b8865d7 100644
--- a/drivers/staging/greybus/debugfs.c
+++ b/drivers/staging/greybus/debugfs.c
@@ -29,3 +29,9 @@
 	debugfs_remove_recursive(gb_debug_root);
 	gb_debug_root = NULL;
 }
+
+struct dentry *gb_debugfs_get(void)
+{
+	return gb_debug_root;
+}
+EXPORT_SYMBOL_GPL(gb_debugfs_get);