configs: fs.py remove --generate-dtb and enable it by default

The option is now enabled if neither --bare-metal nor --dtb-filename are
given.

This is what fs_bigLITTLE.py already did before this patch.

Change-Id: I9179f8c9fa18edbd1e0f1a65ea2c1de0a26b7921
Reviewed-on: https://gem5-review.googlesource.com/c/15899
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>
Maintainer: Jason Lowe-Power <jason@lowepower.com>

configs/common/Options.py

@@ -363,8 +363,6 @@ def addFSOptions(parser):
         parser.add_option("--enable-context-switch-stats-dump", \
                 action="store_true", help="Enable stats dump at context "\
                 "switches and dump tasks file (required for Streamline)")
-        parser.add_option("--generate-dtb", action="store_true", default=False,
-                    help="Automatically generate a dtb file")
 
     # Benchmark options
     parser.add_option("--dual", action="store_true",