Regression: Update the regress script after SE/FS merge
Regression: Update the regress script after SE/FS merge

This patch updates the regress script to reflect the merge of the
SE/FS builds and the new structure of the test directories. It adds a
"mode" flag to the script, that defaults to both se and fs.

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