[SystemC] SCModuleOp::getPortsOfDirection(direction) only returns first occurence

[maerhart]

Above mentioned member function seems to only return the first port of the given direction for some reason. There is no regression test with more than one output port, thus at least one should be added. Observed in the hw.output lowering in HWToSystemC at 9384dccab8692086c21a4166c5e5181623695d91