nvme: introduce bit 5 for critical warning

According to NVM Express v1.4, Section 5.14.1.2 ("SMART / Health
Information"), introduce bit 5 for "Persistent Memory Region has become
read-only or unreliable".
Signed-off-by: Nzhenwei pi <pizhenwei@bytedance.com>
[k.jensen: minor brush ups in commit message]
Signed-off-by: NKlaus Jensen <k.jensen@samsung.com>

include/block/nvme.h

@@ -789,6 +789,7 @@ enum NvmeSmartWarn {
     NVME_SMART_RELIABILITY            = 1 << 2,
     NVME_SMART_MEDIA_READ_ONLY        = 1 << 3,
     NVME_SMART_FAILED_VOLATILE_MEDIA  = 1 << 4,
+    NVME_SMART_PMR_UNRELIABLE         = 1 << 5,
 };
 
 typedef struct NvmeEffectsLog {