[nrf52840] make sure nrf_mbr.h is in include path (#3330)
[nrf52840] make sure nrf_mbr.h is in include path (#3330)


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