nvme: zns: Simplify nvme_zone_parse_entry()

Instead of passing a pointer to a struct nvme_ctrl and a pointer to a
struct nvme_ns_head as the first two arguments of
nvme_zone_parse_entry(), pass only a pointer to a struct nvme_ns as both
the controller structure and ns head structure can be infered from the
namespace structure.

Signed-off-by: Damien Le Moal <dlemoal@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Keith Busch <kbusch@kernel.org>