Current count, from CMTS initialization, of all minislots
defined for this upstream logical channel. This count includes
all IUCs and SIDs, even those allocated to the NULL SID for
a 2.0 logical channel which is inactive.
This is the 64 bit version of docsIfCmtsUpChnlCtrTotalMslots,
and will not be accessible to SNMPv1 managers.
Support for this object is mandatory.