hw/nvme: fix namespace atomic parameter setup

hw/nvme: fix namespace atomic parameter setup

Coverity complains about a possible copy-paste error in the verification
of the namespace atomic parameters (CID 1642811). While the check is
correct, the code (and the intention) is unclear.

Fix this by reworking how the parameters are verified. Peter also
identified that the realize function was not correctly erroring out if
parameters were misconfigured, so fix that too.

Lastly, change the error messages to be more describing.

Coverity: CID 1642811
Fixes: bce51b83709b ("hw/nvme: add atomic boundary support")
Fixes: 3b41acc96299 ("hw/nvme: enable ns atomic writes")
Reviewed-by: Jesper Wendel Devantier <foss@defmacro.it>
Signed-off-by: Klaus Jensen <k.jensen@samsung.com>