Allow selection of the voltage level for the TOFE connector

[mithro]

Currently the VCCIO for the bank connected to the TOFE connector is connected to VCC3V3. It would be nice if we could allow the TOFE connector to be supplied via the other VCC supplies (IE VCC1V5 and VCC1V2). Care would need to be taken to not adversely affect the parts already powered by these supplies.

The TOFE specification would need to be updated to include information about VCCIO stuff.

It would be best if the VCCIO voltage level was controllable / changeable via the FPGA itself. Otherwise a jumper would be another solution. In either case, it voltage level in use should be measurable / detectable via some means.