The value indicating whether the port is capable
of allowing the user to configure receive buffer to
buffer credit.
The values configured for the objects:
fcIfAdminRxBbCredit, fcIfAdminRxBbCreditModeISL,
fcIfAdminRxBbCreditModeFx will take effect
only if the value of this object is true(1),
otherwise the default values specified by the
objects: fcIfCapRxBbCreditDefault,
fcIfCapISLRxBbCreditDefault will stay in effect
depending on the operating mode of the port.