hw/nvme: add basic endurance group support

Add the mandatory Endurance Group identify data structures and log
pages.

For now, all namespaces in a subsystem belongs to a single Endurance
Group.

Reviewed-by: Keith Busch <kbusch@kernel.org>
Signed-off-by: Klaus Jensen <k.jensen@samsung.com>

hw/nvme/nvme.h

@@ -45,6 +45,10 @@ typedef struct NvmeBus {
     OBJECT_CHECK(NvmeSubsystem, (obj), TYPE_NVME_SUBSYS)
 #define SUBSYS_SLOT_RSVD (void *)0xFFFF
 
+typedef struct NvmeEnduranceGroup {
+    uint8_t event_conf;
+} NvmeEnduranceGroup;
+
 typedef struct NvmeSubsystem {
     DeviceState parent_obj;
     NvmeBus     bus;