[dom] Fix API docs in DOM methods

Fix defining params of following methods.

* [setStyle()](http://yuilibrary.com/yui/docs/api/classes/DOM.html#method_setStyle)
* [getStyle()](http://yuilibrary.com/yui/docs/api/classes/DOM.html#method_getStyle)
* [setStyles()](http://yuilibrary.com/yui/docs/api/classes/DOM.html#method_setStyles)
* [getComputedStyle()](http://yuilibrary.com/yui/docs/api/classes/DOM.html#method_getComputedStyle)