memory: constify memory_region_name

It doesn't change the MR and some prospective call sites will have
const MRs at hand.
Signed-off-by: NPeter Crosthwaite <peter.crosthwaite@xilinx.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

include/exec/memory.h

@@ -511,7 +511,7 @@ void memory_region_unregister_iommu_notifier(Notifier *n);
  *
  * @mr: the memory region being queried
  */
-const char *memory_region_name(MemoryRegion *mr);
+const char *memory_region_name(const MemoryRegion *mr);
 
 /**
  * memory_region_is_logging: return whether a memory region is logging writes

memory.c

@@ -1308,7 +1308,7 @@ uint64_t memory_region_size(MemoryRegion *mr)
     return int128_get64(mr->size);
 }
 
-const char *memory_region_name(MemoryRegion *mr)
+const char *memory_region_name(const MemoryRegion *mr)
 {
     return mr->name;
 }