[posix-app] discard received HDLC frame on error (#3394)
[posix-app] discard received HDLC frame on error (#3394)

This commit changes the `HdlcInterface::HandleHdlcFrame()` callback
which handles a received and decoded HDLC frame such that it
discards a bad/incorrect frame from the multi frame buffer (i.e,
discard the frame on any error).
openthread/openthread,erja-gp/openthread,lanyuwen/openthread,openthread/openthread,librasungirl/openthread,turon/openthread,librasungirl/openthread,jwhui/openthread,srickardti/openthread,librasungirl/openthread,bukepo/openthread,bukepo/openthread,abtink/openthread,abtink/openthread,librasungirl/openthread,turon/openthread,lanyuwen/openthread,lanyuwen/openthread,chshu/openthread,erja-gp/openthread,erja-gp/openthread,chshu/openthread,turon/openthread,erja-gp/openthread,turon/openthread,chshu/openthread,openthread/openthread,lanyuwen/openthread,bukepo/openthread,chshu/openthread,chshu/openthread,abtink/openthread,erja-gp/openthread,chshu/openthread,abtink/openthread,srickardti/openthread,lanyuwen/openthread,erja-gp/openthread,lanyuwen/openthread,jwhui/openthread,jwhui/openthread,srickardti/openthread,jwhui/openthread,openthread/openthread,bukepo/openthread,srickardti/openthread