nvme: fix the NVME_ID_NS_NVM_STS_MASK definition

As per NVMe command set specification 1.0c Storage tag size is 7 bits.

Fixes: 4020aad8 ("nvme: add support for enhanced metadata")
Signed-off-by: Ankit Kumar <ankit.kumar@samsung.com>
Reviewed-by: Kanchan Joshi <joshi.k@samsung.com>
Signed-off-by: Keith Busch <kbusch@kernel.org>