ETH_0 needs to be defined even if PLATFORM_SUPPORT_ETHERNET is OFF

[rolandreichweinbmw]

Since the addition of DoIP (commit 7018186), the build breaks if ETH_0 is not defined in case PLATFORM_SUPPORT_ETHERNET is OFF:

libs/bsw/transportRouterSimple/src/transport/routing/TransportRouterSimple.cpp:121:38: error: no member named 'ETH_0' in namespace 'busid'
  121 |     else if (sourceBusId == ::busid::ETH_0)

[rolandreichweinbmw]

Maybe add an #ifdef around that code? In order to prevent ETH_0 etc. to be necessary in projects without ethernet?