Remove bitchar_to_idx() function in tgt-vvp/vvp_process.c
Remove bitchar_to_idx() function in tgt-vvp/vvp_process.c

This function is no longer used and was likely replaced with a
different scheme, so serves no useful purpose.

themperek/iverilog,themperek/iverilog,CastMi/iverilog,CastMi/iverilog,themperek/iverilog,CastMi/iverilog