memory: Correctly return alias region type

Since memory region aliases are neither rom nor ram, they are
described as i/o, which is often incorrect. Return instead the
type of the original region we are aliasing.

Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>

memory.c

@@ -2819,6 +2819,9 @@ void address_space_destroy(AddressSpace *as)
 
 static const char *memory_region_type(MemoryRegion *mr)
 {
+    if (mr->alias) {
+        return memory_region_type(mr->alias);
+    }
     if (memory_region_is_ram_device(mr)) {
         return "ramd";
     } else if (memory_region_is_romd(mr)) {