Because our disk.sys doesn't do anything related to PnP
(compared to disk_new.sys), forcibly declare our partitions
to the MountMgr so that it can references them and assign
them a DOS drive letter on demand later on.
This is needed in order to avoid an infinite recursive loop between
disk!UpdateRemovableGeometry() and ntos!IoReadPartitionTable().
This does not happen with NT5+ disk_new.sys because it doesn't call
IoReadPartitionTable() in that situation.
In spite of what was implemented in our NT DDK sample, this is a legit operation.
This may have been turned legit starting NT5 (reminder, our implementation is
NT4 based...). So, in this situation, just return the information about the whole
disk (and not a random size) and also, mark everything with default values.
See disk_new for an example of how it works in NT5+.
CORE-14124
