[notifier] define 'kEventStrings[]' as const pointer (#5673)
[notifier] define 'kEventStrings[]' as const pointer (#5673)


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