cxl/mem: Drop @host argument to devm_cxl_add_memdev()

cxl/mem: Drop @host argument to devm_cxl_add_memdev()

In all cases the device that created the 'struct cxl_dev_state' instance is
also the device to host the devm cleanup of devm_cxl_add_memdev(). This
simplifies the function prototype, and limits a degree of freedom of the
API.

Cc: Smita Koralahalli <Smita.KoralahalliChannabasappa@amd.com>
Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>
Reviewed-by: Alison Schofield <alison.schofield@intel.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Reviewed-by: Ben Cheatham <benjamin.cheatham@amd.com>
Tested-by: Alejandro Lucero <alucerop@amd.com>
Link: https://patch.msgid.link/20251216005616.3090129-6-dan.j.williams@intel.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Dave Jiang <dave.jiang@intel.com>