cxl: Add helper to delete dport

cxl: Add helper to delete dport

Refactor the code in reap_dports() out to provide a helper function that
reaps a single dport. This will be used later in the cleanup path for
allocating a dport. Renaming to del_port() and del_dports() to mirror
devm_cxl_add_dport().

[dj] Fixed up subject per Robert

Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>
Reviewed-by: Li Ming <ming.li@zohomail.com>
Reviewed-by: Alison Schofield <alison.schofield@intel.com>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Tested-by: Robert Richter <rrichter@amd.com>
Signed-off-by: Dave Jiang <dave.jiang@intel.com>