systemc: Fix the default width values for the various sc_trace-s.

systemc: Fix the default width values for the various sc_trace-s.

These were all set to 8 * sizeof(char) instead of using the size of the
actual data type being traced.

Also add a very simple implementation to the generic sc_signal_in_if<T>
sc_trace which just delegates to the sc_trace of the underlying type T.

Change-Id: I129df46ef9d49705dc3dac76e30c0a3652c981eb
Reviewed-on: https://gem5-review.googlesource.com/c/12818
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>