SE/FS: Put platform pointers in fewer objects.

Not all objects need a platform pointer, and having one creates a dependence
on their being a platform object. This change removes the platform pointer to
from the base device object and moves it into subclasses that actually need
it.

src/dev/baddev.cc

@@ -39,7 +39,6 @@
 #include "base/trace.hh"
 #include "config/the_isa.hh"
 #include "dev/baddev.hh"
-#include "dev/platform.hh"
 #include "mem/port.hh"
 #include "params/BadDevice.hh"
 #include "sim/system.hh"