systemc: Remove the TLM dependence on a non-standard method.

systemc: Remove the TLM dependence on a non-standard method.

The sc_event_finder class in Accellera's implementation has a
non-standard report_error function that it uses internally. The TLM
headers were calling that function in their own event finder subclass.
This change replaces that call with what should be an equivalent bit of
code which is based on the report_error implementation.

Change-Id: Id57d26791df01403a77e70d5f4a00f650dc33599
Reviewed-on: https://gem5-review.googlesource.com/c/15063
Reviewed-by: Anthony Gutierrez <anthony.gutierrez@amd.com>
Maintainer: Anthony Gutierrez <anthony.gutierrez@amd.com>