x86: provide stub for memory_type_changed

Jan indicated that for PV guests the memory type is not changed, for
HVM guests memory_type_changed is needed for EPT's effective memory
type calculation.  This means memory_type_changed is HVM only.

Provide a stub to minimise code churn.

Signed-off-by: Wei Liu <wei.liu2@citrix.com>
Acked-by: Jan Beulich <jbeulich@suse.com>

xen/include/asm-x86/mtrr.h

@@ -92,7 +92,12 @@ extern bool_t mtrr_fix_range_msr_set(struct domain *, struct mtrr_state *,
                                      uint32_t row, uint64_t msr_content);
 extern bool_t mtrr_def_type_msr_set(struct domain *, struct mtrr_state *,
                                     uint64_t msr_content);
+#ifdef CONFIG_HVM
 extern void memory_type_changed(struct domain *);
+#else
+static inline void memory_type_changed(struct domain *d) {}
+#endif
+
 extern bool_t pat_msr_set(uint64_t *pat, uint64_t msr);
 
 bool is_var_mtrr_overlapped(const struct mtrr_state *m);