cxl/core: cxl_mem_sanitize() cleanup

In cxl_mem_sanitize(), the down_read() and up_read() for
cxl_region_rwsem can be simply replaced by a guard(rwsem_read), and the
local variable 'rc' can be removed.

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/20250221012453.126366-3-ming.li@zohomail.com
Signed-off-by: Dave Jiang <dave.jiang@intel.com>

Author: MingLi-4

drivers/cxl/core/mbox.c

@@ -1222,23 +1222,19 @@ int cxl_mem_sanitize(struct cxl_memdev *cxlmd, u16 cmd)
 {
 	struct cxl_memdev_state *mds = to_cxl_memdev_state(cxlmd->cxlds);
 	struct cxl_port  *endpoint;
-	int rc;
 
 	/* synchronize with cxl_mem_probe() and decoder write operations */
 	guard(device)(&cxlmd->dev);
 	endpoint = cxlmd->endpoint;
-	down_read(&cxl_region_rwsem);
+	guard(rwsem_read)(&cxl_region_rwsem);
 	/*
 	 * Require an endpoint to be safe otherwise the driver can not
 	 * be sure that the device is unmapped.
 	 */
 	if (endpoint && cxl_num_decoders_committed(endpoint) == 0)
-		rc = __cxl_mem_sanitize(mds, cmd);
-	else
-		rc = -EBUSY;
-	up_read(&cxl_region_rwsem);
+		return __cxl_mem_sanitize(mds, cmd);
 
-	return rc;
+	return -EBUSY;
 }
 
 static int add_dpa_res(struct device *dev, struct resource *parent,