[cli-uart] save space for NULL terminator in rx buffer (#3500)
[cli-uart] save space for NULL terminator in rx buffer (#3500)


jwhui/openthread,bukepo/openthread,lanyuwen/openthread,jwhui/openthread,openthread/openthread,lanyuwen/openthread,openthread/openthread,lanyuwen/openthread,erja-gp/openthread,abtink/openthread,jwhui/openthread,librasungirl/openthread,srickardti/openthread,turon/openthread,erja-gp/openthread,librasungirl/openthread,lanyuwen/openthread,abtink/openthread,chshu/openthread,erja-gp/openthread,jwhui/openthread,lanyuwen/openthread,abtink/openthread,librasungirl/openthread,abtink/openthread,srickardti/openthread,turon/openthread,erja-gp/openthread,turon/openthread,bukepo/openthread,chshu/openthread,erja-gp/openthread,openthread/openthread,srickardti/openthread,erja-gp/openthread,bukepo/openthread,chshu/openthread,lanyuwen/openthread,chshu/openthread,bukepo/openthread,turon/openthread,srickardti/openthread,chshu/openthread,chshu/openthread,librasungirl/openthread,openthread/openthread