Can I can control an RC servo using only a 5VDC and GND signal?
I doubt that it would work the way you want. In most analog servos, the input pulses trigger an internal multivibrator that's controlled by the feedback pot, and the resulting pulse is combined using some simple logic with the original pulse to drive the motor H-bridge &mdash; the difference in pulse widths drives the motor one way or the other until they are equal.

If you don't provide a stream of pulses, the motor drive will never get activated.

Why not just use a regular DC motor along with some limit switches?