If you want to prepare to become a successful photographer, then I would study a subject that you would want to photograph. Perhaps it is architecture, people and cultures (anthropology, sociology), geography, economics, history, the sciences.... ? But if you know something about a subject then you'd be better equipped to become the master of photographing it.
Salgado was an economist. It probably helped make him a great documentary photojournalist.
But spending four years to learn a skill, like photography, seems rather narrow and about three years too many. If you are passionate about photography, you will learn it on your own.
Of course if you are passionate about any subject you're luckier than most students, who seem to be only going through the motions to please their parents and expectations. Silly kids.
If you need a job to make a decent living while you develop as a photographer, some skilled jobs are somewhat recession-proof. Think in terms of being a plumber, which people will need as long as there is a civilization. When I was a ski bum, the plumber was the smartest guy in town - he only worked a few days a week, odd hours, made great money and could ski everyday.
Think in terms of demographics and the economy... I wouldn't want to be building homes right now, but maintenance of older homes will always be a viable business. Also consider that our population is aging and they will be the best customers, since the wealth is in their hands.
Industrial Design, including car design, is a hot college major right now. Colleges are in business to fill seats, and they love foreign students from well-off families who pay full-priced tuition. This does not mean that they have your best interests at heart and can place you in a career -- so I would consider all these things... automotive design may not be a "safe" major.