Low current to HS gate drive in DRV8825 typical application diagram
VCP is the power supply for the high side gates and which is generated from a charge pump.  It is a voltage higher than VM sufficient so that the high side MOSFET gates can turn on.

The resistor most likely ensures that the capacitor will be discharged (VCP to zero) when power is removed and re-energized so that the high side FET power supply is voltage during power up when the internal circuitry is in an undefined state.