cxl/port: Convert to use ERR_CAST()

Use ERR_CAST() as it is designed for casting an error pointer to
another type.

This macro utilizes the __force and __must_check modifiers, which instruct
the compiler to verify for errors at the locations where it is employed.

Signed-off-by: Yuesong Li <liyuesong@vivo.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Alison Schofield <alison.schofield@intel.com>
Link: https://patch.msgid.link/20240829125235.3266865-1-liyuesong@vivo.com
Signed-off-by: Dave Jiang <dave.jiang@intel.com>

Author: Yuesong Li

drivers/cxl/core/port.c

@@ -941,7 +941,7 @@ struct cxl_root *devm_cxl_add_root(struct device *host,
 
 	port = devm_cxl_add_port(host, host, CXL_RESOURCE_NONE, NULL);
 	if (IS_ERR(port))
-		return (struct cxl_root *)port;
+		return ERR_CAST(port);
 
 	cxl_root = to_cxl_root(port);
 	cxl_root->ops = ops;