exec: introduce cpu_reload_memory_map

This for now is a simple TLB flush.  This can change later for two
reasons:

1) an AddressSpaceDispatch will be cached in the CPUState object

2) it will not be possible to do tlb_flush once the TCG-generated code
runs outside the BQL.

Reviewed-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

exec.c

@@ -2026,7 +2026,7 @@ static void tcg_commit(MemoryListener *listener)
         if (cpu->tcg_as_listener != listener) {
             continue;
         }
-        tlb_flush(cpu, 1);
+        cpu_reload_memory_map(cpu);
     }
 }