systemc: Stop explicitly adding the systemc ext dir to CPPPATH.

That's now handled automatically when the native systemc API is
enabled.

Change-Id: If1f88929af335a40554a9fd8df6f68aa1a4c0ba4
Reviewed-on: https://gem5-review.googlesource.com/c/14398
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Maintainer: Gabe Black <gabeblack@google.com>
1 file changed