Fix non power of 2 mux gen

[KelvinChung2000]

Now the mux gen should be correct for the non-power of 2 muxes.

 //switch matrix multiplexer E2BEGb6 MUX-5
assign E2BEGb6_input = {W6END1,WW4END9,WW4END1,W2END1,W2END0};
cus_mux81_buf inst_cus_mux81_buf_E2BEGb6 (
    .A0(E2BEGb6_input[0]),
    .A1(E2BEGb6_input[1]),
    .A2(E2BEGb6_input[2]),
    .A3(E2BEGb6_input[3]),
    .A4(E2BEGb6_input[4]),
    .A5(GND0),
    .A6(GND0),
    .A7(GND0),
    .S0(ConfigBits[32+0]),
    .S0N(ConfigBits_N[32+0]),
    .S1(ConfigBits[32+1]),
    .S1N(ConfigBits_N[32+1]),
    .S2(ConfigBits[32+2]),
    .S2N(ConfigBits_N[32+2]),
    .X(E2BEGb6)
);