Each NvmeNamespace can be used by serveral controllers,
but a NvmeNamespace can at most belong to a single NvmeSubsystem.
Store a pointer to the NvmeSubsystem, if the namespace was realized
with a NvmeSubsystem.
Reviewed-by: Keith Busch <kbusch@kernel.org>
Signed-off-by: Niklas Cassel <niklas.cassel@wdc.com>
Signed-off-by: Klaus Jensen <k.jensen@samsung.com>
534a93d3a0