sparc: Return debug faults from unimplemented instructions.

These had been marked as non-speculative so that their execute
functions would only be called if the instruction should really be
executed. Instead, we can return faults which will cause the same
behavior when the instruction is committed and let the instruction
execute as normal.

Change-Id: I39fa5073e93399424144724b99bdc12070e42286
Reviewed-on: https://gem5-review.googlesource.com/5465
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

sparc: Pull the unimplemented formats out of the ISA description.

These are simple classes which don't need to be in the ISA description.

Change-Id: Ia0bb45f50c4da2536855efcb3c17c7780b431332
Reviewed-on: https://gem5-review.googlesource.com/5464
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>