cxl: Move devm_cxl_add_nvdimm_bridge() to cxl_pmem.ko

cxl: Move devm_cxl_add_nvdimm_bridge() to cxl_pmem.ko

Moving the symbol devm_cxl_add_nvdimm_bridge() to
drivers/cxl/cxl_pmem.c, so that cxl_pmem can export a symbol that gives
cxl_acpi a depedency on cxl_pmem kernel module. This is a prepatory patch
to resolve the issue of a race for nvdimm_bus object that is created
during cxl_acpi_probe().

No functional changes besides moving code.

Suggested-by: Dan Williams <dan.j.williams@intel.com>
Acked-by: Ira Weiny <ira.weiny@intel.com>
Tested-by: Alison Schofield <alison.schofield@intel.com>
Reviewed-by: Alison Schofield <alison.schofield@intel.com?>
Link: https://patch.msgid.link/20260205001633.1813643-2-dave.jiang@intel.com
Signed-off-by: Dave Jiang <dave.jiang@intel.com>