cxl: Introduce put_cxl_root() helper

Add a helper function put_cxl_root() to maintain symmetry for
find_cxl_root() function instead of relying on open coding of the
put_device() in order to dereference the 'struct device' that happens via
get_device() in find_cxl_root().

Suggested-by: Robert Richter <rrichter@amd.com>
Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Reviewed-by: Robert Richter <rrichter@amd.com>
Link: https://lore.kernel.org/r/170449245417.3779673.4566146351673989387.stgit@djiang5-mobl3
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

drivers/cxl/core/port.c

@@ -986,6 +986,15 @@ struct cxl_port *find_cxl_root(struct cxl_port *port)
 }
 EXPORT_SYMBOL_NS_GPL(find_cxl_root, CXL);
 
+void put_cxl_root(struct cxl_root *cxl_root)
+{
+	if (!cxl_root)
+		return;
+
+	put_device(&cxl_root->port.dev);
+}
+EXPORT_SYMBOL_NS_GPL(put_cxl_root, CXL);
+
 static struct cxl_dport *find_dport(struct cxl_port *port, int id)
 {
 	struct cxl_dport *dport;

drivers/cxl/cxl.h

@@ -735,6 +735,9 @@ struct cxl_port *devm_cxl_add_port(struct device *host,
 struct cxl_root *devm_cxl_add_root(struct device *host,
 				   const struct cxl_root_ops *ops);
 struct cxl_port *find_cxl_root(struct cxl_port *port);
+void put_cxl_root(struct cxl_root *cxl_root);
+DEFINE_FREE(put_cxl_root, struct cxl_root *, if (_T) put_cxl_root(_T))
+
 int devm_cxl_enumerate_ports(struct cxl_memdev *cxlmd);
 void cxl_bus_rescan(void);
 void cxl_bus_drain(void);