dimm: Correct type of MemoryHotplugState->base

The 'base' field of MemoryHotplugState is ram_addr_t, which indicates that
it exists in the abstract address space of RAM regions.

However, the actual usage of this field indicates that it is a concrete
physical address (it's passed as an offset to memory_region_add_subgregion
for example).

So, correct its type to 'hwaddr'.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Igor Mammedov <imammedo@redhat.com>
Acked-by: Eduardo Habkost <ehabkost@redhat.com>

include/hw/mem/pc-dimm.h

@@ -77,7 +77,7 @@ typedef struct PCDIMMDeviceClass {
  * @mr: hotplug memory address space container
  */
 typedef struct MemoryHotplugState {
-    ram_addr_t base;
+    hwaddr base;
     MemoryRegion mr;
 } MemoryHotplugState;