Since that is clearly an absurd statement, I will give him the benefit of the doubt and assume he meant that nothing the president does is legally considered a conflict of interest. In otherwords, the specific laws against conflicts of interest do not apply to the president.
This turns out to be a suprisingly true statement. The only conflict of interest law I could find (after an admitadly brief search) is [0].
I have not thourally reviewed it, but found the following snippet in the definitions section:
"Except as otherwise provided in such sections, the terms “officer” and “employee” in sections 203, 205, 207 through 209, and 218 of this title shall not include the President, the Vice President, a Member of Congress, or a Federal judge." [1].
[0] https://www.law.cornell.edu/uscode/text/18/part-I/chapter-11
Sounds like you already know this, but the current president-elect just said the same thing:
http://www.philly.com/philly/blogs/attytood/When-the-preside...
“The law’s totally on my side," the president-elect told the Times. "The president can’t have a conflict of interest.” Translation: When this president does it, that means it is not illegal. Unlike Nixon, however, I'm starting to worry that Trump's going to get away with this.