DPST switch control 5vDC and 220vAC
simulate this circuit &ndash; Schematic created using CircuitLab

Figure 1. Two-way switching circuit.

Mixing mains and low voltage on the one switch isn't recommended. You can achieve what you want with a two-way switching circuit as shown in Figure 1. The PSU (represented by a transformer in the schematic) will be on if both switches are up or both are down. These type of switches are called "3-way" in North America.