mem: Get rid of some stray lines which ended up in packet.hh.

These were left in by mistake when refactoring patches for review.

Change-Id: I4c39b5a3e2a2d3957e725a6ffcf48c25b8a69f2e
Reviewed-on: https://gem5-review.googlesource.com/c/13495
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

src/mem/packet.hh

@@ -1077,11 +1077,9 @@ class Packet : public Printable
     template <typename T>
     void set(T v, ByteOrder endian);
 
-#if THE_ISA != NULL_ISA
     /** Set the value in the data pointer to v as guest endian. */
     template <typename T>
     void set(T v);
-#endif
 
 
     /**