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.

haowu4682/gem5,haowu4682/gem5,LingxiaoJIA/gem5,haowu4682/gem5,LingxiaoJIA/gem5,LingxiaoJIA/gem5,haowu4682/gem5,haowu4682/gem5,LingxiaoJIA/gem5,LingxiaoJIA/gem5,haowu4682/gem5,haowu4682/gem5,LingxiaoJIA/gem5,haowu4682/gem5,haowu4682/gem5,LingxiaoJIA/gem5