systemc: Adjust some whitespace in a print out.

This makes a test output file diff successfully.

Change-Id: Ia269b4b33f719a2559197d9296f9acc601ec65f7
Reviewed-on: https://gem5-review.googlesource.com/12062
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

src/systemc/dt/int/sc_nbcommon.inc

@@ -2580,7 +2580,7 @@ CLASS_TYPE::dump(::std::ostream &os) const
 
     os << "width = " << length() << ::std::endl;
     os << "value = " << *this << ::std::endl;
-    os << "bits = ";
+    os << "bits  = ";
 
     int len = length();