sim: Remove some old transitional code in SEWorkload.

This code was just to catch cases where the SEWorkload init_compatible
function couldn't find a compatible SEWorkload subclass. Now that all of
these classes are set up with this mechanism, there's no need to keep
this code around.

Change-Id: Ie847f5a90ccf98eb58c149a22a6881529344946d
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/52107
Reviewed-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Maintainer: Giacomo Travaglini <giacomo.travaglini@arm.com>
Tested-by: kokoro <noreply+kokoro@google.com>

src/sim/Workload.py

@@ -102,10 +102,6 @@ class SEWorkload(Workload, metaclass=SEWorkloadMeta):
         if len(options) > 1:
             raise ValueError("More than one SE workload is compatible with %s")
         elif len(options) < 1:
-            # For now, fall back to the base class if there are no matches.
-            # After we've had a chance to implement everything, this default
-            # can be removed since this should always find exactly one match.
-            return SEWorkload(*args, **kwargs)
             raise ValueError("No SE workload is compatible with %s", path)
 
         return options[0](*args, **kwargs)