Yes, Trump should be forced to give up his share in the Dakota Access company due to conflict of interest. He should also give up financial interest in other companies for the same reason. A president can not be expected to make unbiased decisions when he has a personal interest in the outcome.
Trump should sell his shares in the Dakota access company building the pipeline because it is a conflict of interest. The United States government is in a confrontation with Native Americans over the pipeline route and Trump's financial interest is in crushing the protests and building the pipeline under Indian lands.
Trump is not the first person with assets to become President. It is impractical to expect someone to just give away all of their assets and net worth the day they get elected into office. Instead, these things are put into a trust and managed by others while the person is in office. This is fair to everyone.
Stock in Dakota Access could be placed in a blind trust so that Trump would have no way to profit from it as a result of decisions he makes as President. Owning this stock would only be a conflict of interest if he made decisions based on whether he would make a profit on the stock.