serial-parsers: also match responses that are not at end of line

Accepts an AT command response even if additional data is provided. This is necessary during AT port probing since no URC parsers are installed and probing fails if additional data is returned. The rest of the response is ignored during AT port probing. Contributes to #194

Resuming is still not fast enough, it takes 2 rings on the caller side before the PinePhone starts ringing. Although, before this patch it took 3 rings. So #194 cannot be closed yet.