systemc,util: Update sc_master_port.cc now that params() returns a ref.

The params() methods (when they exist) now all return references instead
of pointers. Update sc_master_port.cc to work with this.

Change-Id: Ifa3c33e69ba9c16dc2b984784e7978b43714dbf2
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/42585
Reviewed-by: Bobby R. Bruce <bbruce@ucdavis.edu>
Maintainer: Bobby R. Bruce <bbruce@ucdavis.edu>
Tested-by: kokoro <noreply+kokoro@google.com>

util/tlm/src/sc_master_port.cc

@@ -93,8 +93,7 @@ SCMasterPort::SCMasterPort(const std::string& name_,
     transactor(nullptr),
     simControl(simControl)
 {
-    system =
-        dynamic_cast<const ExternalMasterParams*>(owner_.params())->system;
+    system = dynamic_cast<const ExternalMasterParams&>(owner_.params()).system;
 }
 
 void