nvme: check ns's volatile write cache not present

When the VWC of a namespace does not exist, the BLK_FEAT_WRITE_CACHE
flag should not be set when registering the block device, regardless
of whether the controller supports VWC.

Signed-off-by: Guixin Liu <kanie@linux.alibaba.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Keith Busch <kbusch@kernel.org>

include/linux/nvme.h

@@ -564,6 +564,7 @@ enum {
 	NVME_NS_FLBAS_META_EXT	= 0x10,
 	NVME_NS_NMIC_SHARED	= 1 << 0,
 	NVME_NS_ROTATIONAL	= 1 << 4,
+	NVME_NS_VWC_NOT_PRESENT = 1 << 5,
 	NVME_LBAF_RP_BEST	= 0,
 	NVME_LBAF_RP_BETTER	= 1,
 	NVME_LBAF_RP_GOOD	= 2,