cxl/core: Use guard() to drop the goto pattern of cxl_dpa_free()

cxl_dpa_free() has a goto pattern to call up_write() for cxl_dpa_rwsem,
it can be removed by using a guard() to replace the down_write() and
up_write().

Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Reviewed-by: Alison Schofield <alison.schofield@intel.com>
Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Acked-by: Davidlohr Bueso <dave@stgolabs.net>
Signed-off-by: Li Ming <ming.li@zohomail.com>
Link: https://patch.msgid.link/20250221012453.126366-5-ming.li@zohomail.com


Signed-off-by: Dave Jiang <dave.jiang@intel.com>