nvme: stop using AWUPF

As described at [0], much of the atomic write parts of the specification
are lacking.

For now, there is nothing which we can do in software about the lack of
a dedicated NVMe write atomic command.

As for reading the atomic write limits, it is felt that the per-namespace
values are mostly properly specified and it is assumed that they are
properly implemented.

The specification of NAWUPF is quite clear. However the specification of
NABSPF is less clear. The lack of clarity in NABSPF comes from deciding
whether NABSPF applies when NSABP is 0 - it is assumed that NSABPF does
not apply when NSABP is 0.

As for the per-controller AWUPF, how this value applies to shared
namespaces is missing in the specification. Furthermore, the value is in
terms of logical blocks, which is an NS entity.

Since AWUPF is so poorly defined, stop using it already together.
Hopefully this will force vendors to implement NAWUPF support always.

Note that AWUPF not only effects atomic write support, but also the
physical block size reported for the device.

To help users know this restriction, log an info message per NS.

[0] https://lore.kernel.org/linux-nvme/20250707141834.GA30198@lst.de/

Tested-by: Nilay Shroff <nilay@linux.ibm.com>
Reviewed-by: Nilay Shroff <nilay@linux.ibm.com>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: John Garry <john.g.garry@oracle.com>
Signed-off-by: Keith Busch <kbusch@kernel.org>

drivers/nvme/host/nvme.h

@@ -464,6 +464,8 @@ struct nvme_ctrl {
 
 	enum nvme_ctrl_type cntrltype;
 	enum nvme_dctype dctype;
+
+	u16			awupf; /* 0's based value. */
 };
 
 static inline enum nvme_ctrl_state nvme_ctrl_state(struct nvme_ctrl *ctrl)
@@ -496,7 +498,6 @@ struct nvme_subsystem {
 	u8			cmic;
 	enum nvme_subsys_type	subtype;
 	u16			vendor_id;
-	u16			awupf; /* 0's based value. */
 	struct ida		ns_ida;
 #ifdef CONFIG_NVME_MULTIPATH
 	enum nvme_iopolicy	iopolicy;