This object indicates the amount of power available for
the PD to use. This value may differ from the value
cpeExtPsePortPwrAllocated due to the efficiency issues
of delivering the power from the PSE to the PD.
When sufficient power is available to power a PD, this
value should be equal to the lower of the two objects,
cpeExtDefaultAllocation and cpeExtPsePortPwrMax.