cxl/pci: Simplify CDAT retrieval error path

cxl/pci: Simplify CDAT retrieval error path

The cdat.table and cdat.length fields in struct cxl_port are set before
CDAT retrieval and must therefore be unset on failure.

Simplify by setting only on success.

Suggested-by: Jonathan Cameron <Jonathan.Cameron@Huawei.com>
Link: https://lore.kernel.org/linux-cxl/20230209113422.00007017@Huawei.com/
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
[lukas: rebase and rephrase commit message]
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Acked-by: Bjorn Helgaas <bhelgaas@google.com>
Link: https://lore.kernel.org/r/7a5c7104fb6a3016dbaec1c5d0ed34619ea11a0c.1678543498.git.lukas@wunner.de
Signed-off-by: Dan Williams <dan.j.williams@intel.com>