fix cxl_pmem_region_probe bug · Pull Request !4424 · anolis/cloud-kernel

bugzilla: https://bugzilla.openanolis.cn/show_bug.cgi?id=12242

when CXL PMEM probe, it will go like this stack:

```
cxl_mem_driver
  -> cxl_mem_probe()
    -> devm_cxl_add_endpoint()
      -> devm_cxl_add_port()
        -> __devm_cxl_add_port()
          -> device_add(), which triggers the cxl_port_driver probe
            cxl_port_driver
              -> cxl_port_probe()
                -> cxl_endpoint_port_probe()
                  -> construct_region()
                    -> cxl_region_probe()
                      -> cxl_pmem_region_probe() *
          -> set cxlmd->endpoint x
    -> devm_cxl_add_nvdimm() *
      -> cxl_find_nvdimm_bridge() requires cxlmd->endpoint to locate the cxl_nvdimm_bridge x
```
In cxl_mem_probe(), the call to devm_cxl_add_endpoint() triggers device_add(), which in turn triggers cxl_port_probe() and eventually cxl_pmem_region_probe(). 
However, cxl_pmem_region_probe() requires the presence of the cxl_nvdimm structure to execute successfully, and this structure is created by devm_cxl_add_nvdimm().

The current issue is that devm_cxl_add_nvdimm() is called after devm_cxl_add_endpoint() in cxl_mem_probe(). 
This means there is no guarantee that devm_cxl_add_nvdimm() will execute before cxl_pmem_region_probe(). 
As a result, when cxl_pmem_region_probe() runs, it fails to find the cxl_nvdimm structure, leading to the following error:

[  +0.000336] cxl_pmem_region pmem_region0: [2]: mem1: no nvdimm found
[  +0.000003] cxl_pmem_region pmem_region0: probe: -19

To resolve this issue, the call to devm_cxl_add_nvdimm() can be moved into cxl_endpoint_port_probe().
This ensures that cxl_nvdimm is created before cxl_pmem_region_probe() is executed, thereby preventing the failure.
Additionally, the cxlmd->endpoint set operation can be moved before device_add(), ensuring that devm_cxl_add_nvdimm() executes successfully.

```
cxl_mem_driver
  -> cxl_mem_probe()
    -> devm_cxl_add_endpoint()
      -> devm_cxl_add_port()
        -> __devm_cxl_add_port()
          -> set cxlmd->endpoint x
          -> device_add()
            cxl_port_driver
              -> cxl_port_probe()
                -> cxl_endpoint_port_probe()
                  -> devm_cxl_add_nvdimm() *
                    -> cxl_find_nvdimm_bridge() require cxlmd->endpoint to locate the cxl_nvdimm_bridge x
                  -> construct_region()
                    -> cxl_region_probe()
                      -> cxl_pmem_region_probe() *
```

类型	指派人员	状态
审查	Guanjun xunlei zelindeng Guixin Liu	已完成 (0/0人)
测试	小龙已测试通过	已完成 (1/1人)

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