target-i386: use memory API to implement SMRAM

Remove cpu_smm_register and cpu_smm_update.  Instead, each CPU
address space gets an extra region which is an alias of
/machine/smram.  This extra region is enabled or disabled
as the CPU enters/exits SMM.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

target-i386/machine.c

@@ -372,6 +372,9 @@ static int cpu_post_load(void *opaque, int version_id)
     }
     tlb_flush(cs, 1);
 
+    if (tcg_enabled()) {
+        cpu_smm_update(cpu);
+    }
     return 0;
 }