Mismatch between ifDescr and lldpPortDescription for single port devices

In case of Single Port Devices, the Profinet Stack adapts the lldpLocPortDescr object such that it does not contain "Switch". This behavior is not implemented for the ifDescr mib object in the mib database. As a result the Profinet Certification fails due to different names.

The Mib database shall behave in the same way as Profinet Stack does and ommit the "Switch" in case startup parameter ulEthPortCnt is set to 1 or lower.