config: Fix DRAM rank option in sweep script
config: Fix DRAM rank option in sweep script

Align with changes in the common bits.
(transplanted from 062c820aef2435ee4a1540c09e85eded5ce29e05)

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