Clearly the order of operations is immaterial, and no row or column has to be reversed more than once. In effect, then, you're asking if a given matrix of $+1$'s and $-1$'s can be factored as the product of a column vector and a row vector of $+1$'s and $-1$'s. It's easy to see that this is possible just in case any two rows of the matrix are either equal or opposite, and that means that each $2\times2$ submatrix has an even number of each sign, i.e., there is no $2\times2$ submatrix with an odd number of black stones.
The procedure for getting rid of the black stones is very simple: pick a row and make it all-white with column reversals, then reverse all the black rows.