cxl: support Type2 when initializing cxl_dev_state

cxl: support Type2 when initializing cxl_dev_state

In preparation for type2 drivers add function and macro for
differentiating CXL memory expanders (type 3) from CXL device
accelerators (type 2) helping drivers built from public headers
to embed struct cxl_dev_state inside a private struct.

Update type3 driver for using this same initialization.

Signed-off-by: Alejandro Lucero <alucerop@amd.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Reviewed-by: Alison Schofield <alison.schofield@intel.com>
Reviewed-by: Gregory Price <gourry@gourry.net>
Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>
Link: https://patch.msgid.link/20260306164741.3796372-2-alejandro.lucero-palau@amd.com
Signed-off-by: Dave Jiang <dave.jiang@intel.com>