The value of tSyncIfTimingAdmRef2SrcHw specifies the source HW
Index of the second timing reference if the source is not a port.
This can only be set to a valid HW Index if the value of
tSyncIfTimingAdmRef2SrcPort is '1e000000'H.
Setting the value of tSyncIfTimingAdmRef2SrcHw from non-zero to zero
will cause the value of tSyncIfTimingAdmRef2BITSIfType to be reset to
its default value of 't1-esf'.