Fix bug in MDT BITMAP to allow more than 2GB of memory.
Fix bug in MDT BITMAP to allow more than 2GB of memory.

Signed-off by Ali Saidi <saidi@eecs.umich.edu>

andrewfu0325/gem5-aladdin,andrewfu0325/gem5-aladdin,andrewfu0325/gem5-aladdin,andrewfu0325/gem5-aladdin,andrewfu0325/gem5-aladdin,andrewfu0325/gem5-aladdin,andrewfu0325/gem5-aladdin