cxl/region: Cleanup target list on attach error

cxl/region: Cleanup target list on attach error

Jonathan noticed that the target list setup is not unwound completely
upon error. Undo all the setup in the 'err_decrement:' exit path.

Fixes: 27b3f8d13830 ("cxl/region: Program target lists")
Reported-by: Jonathan Cameron <Jonathan.Cameron@Huawei.com>
Link: http://lore.kernel.org/r/20230208123031.00006990@Huawei.com
Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Reviewed-by: Vishal Verma <vishal.l.verma@intel.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Link: https://lore.kernel.org/r/167601996980.1924368.390423634911157277.stgit@dwillia2-xfh.jf.intel.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>