The motherboard does not have an integrated GPU; the spec only means that the PC has an integrated GPU *if* you use an APU and not something like an 880k. Even if it did, it would not support Crossfire in this manner.
It is not a typical Crossfire board in that it only has one PCIEx16 slot. And as this is an entry-level platform, you wouldn't get much of a benefit from multi-GPU solutions. However, it can use Hybrid Crossfire, which is a cross between the 7700k's integrated graphic with an R7 240 or R7 250 (not a 250X). This isn't very good though, you'd still be better off using a 260 or a 270 or a 270X as a single GPU then mucking around with this.