[mgsim-refactor] Sanitize the default configuration.
[mgsim-refactor] Sanitize the default configuration.

- the number of root directories now defaults to 2, to mirror the
  standard profile from the SL runner.

- the base address for the raw configuration data is now 0x2000000,
  because with the previous default of 0x2000 it would grow large
  enough to overlap with the program code at 0x10000.

git-svn-id: c257622338fa90c299bfd3fbe1eee5dac8caa856@4445 e97e5017-a994-416e-809d-76780e9f78db

Bitblade-org/mgsim,Bitblade-org/mgsim,Bitblade-org/mgsim,Bitblade-org/mgsim