systemc: Add some error checks to sc_export.

Change-Id: Ib0c14a5c7dad37b33d61c9b406f6b84121d94e46
Reviewed-on: https://gem5-review.googlesource.com/c/12965
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>
3 files changed