cxl: Fix devm host device for CXL fwctl initialization

cxl: Fix devm host device for CXL fwctl initialization

Testing revealed the following error message for a CXL memdev that has
Feature support:
[   56.690430] cxl mem0: Resources present before probing

Attach the allocation of cxl_fwctl to the parent device of cxl_memdev.
devm_add_* calls for cxl_memdev should not happen before the memdev
probe function or outside the scope of the memdev driver.

cxl_test missed this bug because cxl_test always arranges for the
cxl_mem driver to be loaded before cxl_mock_mem runs. So the driver core
always finds the devres list idle in that case.

[DJ: Updated subject title and added commit log suggestion from djbw]

Fixes: 858ce2f56b52 ("cxl: Add FWCTL support to CXL")
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Reviewed-by: Alison Schofield <alison.schofield@intel.com>
Link: https://lore.kernel.org/linux-cxl/6801aea053466_71fe2944c@dwillia2-xfh.jf.intel.com.notmuch/
Link: https://patch.msgid.link/20250418002933.406439-1-dave.jiang@intel.com
Signed-off-by: Dave Jiang <dave.jiang@intel.com>