Texas Instruments Trims Revenue Estimates  SAN FRANCISCO (Reuters) - Texas Instruments Inc. &lt;A HREF="http://www.investor.reuters.com/FullQuote.aspx?ticker=TXN.N target=/stocks/quickinfo/fullquote"&gt;TXN.N&lt;/A&gt;,  the largest maker of chips for cell phones, trimmed its  third-quarter revenue outlook on Wednesday as customers worked  off inventories of unsold chips, making it the second major  chip supplier to pare third-quarter expectations.