add internal fpga voltage sensor to unb2_minimal

...oard2/designs/unb2_minimal/quartus/qsys_unb2_minimal.qsys

...board2/designs/unb2_minimal/src/vhdl/mmm_unb2_minimal.vhd

...2/designs/unb2_minimal/src/vhdl/qsys_unb2_minimal_pkg.vhd

.../uniboard2/designs/unb2_minimal/src/vhdl/unb2_minimal.vhd