[network-data] use explicit signed int for bit field (#4720)
[network-data] use explicit signed int for bit field (#4720)


lanyuwen/openthread,abtink/openthread,chshu/openthread,abtink/openthread,lanyuwen/openthread,librasungirl/openthread,openthread/openthread,bukepo/openthread,abtink/openthread,bukepo/openthread,lanyuwen/openthread,chshu/openthread,chshu/openthread,bukepo/openthread,lanyuwen/openthread,librasungirl/openthread,lanyuwen/openthread,openthread/openthread,srickardti/openthread,jwhui/openthread,librasungirl/openthread,openthread/openthread,srickardti/openthread,chshu/openthread,bukepo/openthread,chshu/openthread,lanyuwen/openthread,abtink/openthread,librasungirl/openthread,srickardti/openthread,openthread/openthread,srickardti/openthread,jwhui/openthread,jwhui/openthread,jwhui/openthread,chshu/openthread