codegen: drop emit_port_*value funcs
codegen: drop emit_port_*value funcs

Replace `emit_port_lvalue` and `emit_port_rvalue` by calls to
`emit_lvalue` and `emit_rvalue` on `EntityGenerator`, respectively.

fabianschuiki/moore,fabianschuiki/moore,fabianschuiki/moore,fabianschuiki/moore,fabianschuiki/moore