Represents a flow group to traffic class map. The octet
string consists of eight octets, one for each flow group.
The position in the string represents the flow group, where
the first (left-most) position represents flow group 0. The
value of the octet represents the mapped traffic class for
the flow group, where the value of zero represents traffic
class 0 and so on. See ethDevCapMaxTrafficClass for max
value supported by the device.