You don't need a master's degree to become a reporter or editor in any of the different forms of news - print, tv, online. You only need a lot of curiosity and the willingness to work hard.
However, as your career in journalism advances, you may decide to specialize in a specific topic area: politics, business, science, sports, etc. For this, sometimes reporters and editors will get a master's degree in their area so they can expand their expertise and understanding of the subject matter. For instance, if you want to focus on politics you might get a master's degree in political science, or if you want to focus on business reporting you might get a master's of business administration (MBA), or a master's in international relations in order to cover international events or organizations such as the United Nations. This could possibly bring you up to the same educational level as the people whom you are covering in the news.
That said, there is still no better education than simply doing the job. Some of the world's best journalists in their areas have risen through the ranks and become tops in the business by spending every day as a working reporter and/or editor. There are many things you will learn on the job that the classroom can never teach.