pc-dimm: correct comment of MemoryHotplugState

correct comment and remove an unused macro. commit adcb4ee6
already correct its type

Signed-off-by: Cao jin <caoj.fnst@cn.fujitsu.com>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>

include/hw/mem/pc-dimm.h

@@ -20,8 +20,6 @@
 #include "sysemu/hostmem.h"
 #include "hw/qdev.h"
 
-#define DEFAULT_PC_DIMMSIZE (1024*1024*1024)
-
 #define TYPE_PC_DIMM "pc-dimm"
 #define PC_DIMM(obj) \
     OBJECT_CHECK(PCDIMMDevice, (obj), TYPE_PC_DIMM)
@@ -72,7 +70,7 @@ typedef struct PCDIMMDeviceClass {
 
 /**
  * MemoryHotplugState:
- * @base: address in guest RAM address space where hotplug memory
+ * @base: address in guest physical address space where hotplug memory
  * address space begins.
  * @mr: hotplug memory address space container
  */