xen/nospec: Remove unreachable code

When CONFIG_SPECULATIVE_HARDEN_LOCK is active, this reads:

  static always_inline bool lock_evaluate_nospec(bool condition)
  {
      return arch_lock_evaluate_nospec(condition);
      return condition;
  }

Insert an #else to take out the second return.

Fixes: 7ef0084418 ("x86/spinlock: introduce support for blocking speculation into critical regions")
Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Luca Fancellu <luca.fancellu@arm.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>

xen/include/xen/nospec.h

@@ -82,8 +82,9 @@ static always_inline bool lock_evaluate_nospec(bool condition)
 {
 #ifdef CONFIG_SPECULATIVE_HARDEN_LOCK
     return arch_lock_evaluate_nospec(condition);
-#endif
+#else
     return condition;
+#endif
 }
 
 #endif /* XEN_NOSPEC_H */