If reshape is performed on drives larger then 2 TB,
migration checkpoint area that is calculated exeeds 32-bit value.
This checkpoint area is a reserved space threated as backup
during reshape - at the end of the drive, right before metadata.
As a result - wrong space is used and the data that may exists there
is overwritten.
Adding additional field to migration record to track high order 32-bits
of pba of this area. Three other fields that may exceed 32-bit value
for large drives are added as well.