When the value of tmnxPortEtherClockConfig is 'automatic' the
Ethernet interface will automatically negotiate clock mastership
along with other link parameters with the far end. Depending
upon the capabilities of the two ends, one will be master the
other will be slave for clocking.
When the value of tmnxPortEtherClockConfig is 'manual-master', the
Ethernet interface will negotiate other link parameters with the
far end except clock mastership. It assumes clock mastership and want
the other end to be slave.
When the value is 'manual-slave' this ethernet interface chooses to
be slave and wants the far end to assume clock mastership.
For 10 baseT and 100 baseT ethernet interfaces, value of this
variable should be 'none', as this will not be applicable
for those interfaces.