cxl/memdev: Remove unused partition values

cxl/memdev: Remove unused partition values

The next volatile and next persistent values are unused and are
cluttering the cxl_memdev_state.

Remove these values.

Reviewed-by: Davidlohr Bueso <dave@stgolabs.net>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Reviewed-by: Fan Ni <fan.ni@samsung.com>
Signed-off-by: Ira Weiny <ira.weiny@intel.com>
Link: https://patch.msgid.link/20250206-cxl-cleanup-v1-1-9ddf26dd8433@intel.com
Signed-off-by: Dave Jiang <dave.jiang@intel.com>