ds1225y: Drop bogus qdev field from NvRamState

It is not a device, and the field is not used from code either.
Signed-off-by: NAndreas Färber <afaerber@suse.de>

hw/nvram/ds1225y.c

@@ -26,7 +26,6 @@
 #include "trace.h"
 
 typedef struct {
-    DeviceState qdev;
     MemoryRegion iomem;
     uint32_t chip_size;
     char *filename;