Fix a PHPDoc error in FTP Class

The second parameter of the "chmod" method is an octal integer.
diff --git a/system/libraries/Ftp.php b/system/libraries/Ftp.php
index 461e884..76f5e15 100644
--- a/system/libraries/Ftp.php
+++ b/system/libraries/Ftp.php
@@ -445,7 +445,7 @@
 	 * Set file permissions
 	 *
 	 * @param	string	the file path
-	 * @param	string	the permissions
+	 * @param	int	the permissions
 	 * @return	bool
 	 */
 	public function chmod($path, $perm)