drivers/xen/xenbus/xenbus_client.c: fix bugon.cocci warnings

Use BUG_ON instead of a if condition followed by BUG.

Generated by: scripts/coccinelle/misc/bugon.cocci

Reported-by: Zeal Robot <zealci@zte.com.cn>
Signed-off-by: Jing Yangyang <jing.yangyang@zte.com.cn>
Reviewed-by: SeongJae Park <sjpark@amazon.de>
Reviewed-by: Juergen Gross <jgross@suse.com>
Link: https://lore.kernel.org/r/20210825062451.69998-1-deng.changcheng@zte.com.cn
Signed-off-by: Juergen Gross <jgross@suse.com>

Author: Jing Yangyang

drivers/xen/xenbus/xenbus_client.c

@@ -542,8 +542,7 @@ static int __xenbus_map_ring(struct xenbus_device *dev,
 		}
 	}
 
-	if (HYPERVISOR_grant_table_op(GNTTABOP_unmap_grant_ref, info->unmap, j))
-		BUG();
+	BUG_ON(HYPERVISOR_grant_table_op(GNTTABOP_unmap_grant_ref, info->unmap, j));
 
 	*leaked = false;
 	for (i = 0; i < j; i++) {
@@ -581,8 +580,7 @@ static int xenbus_unmap_ring(struct xenbus_device *dev, grant_handle_t *handles,
 		gnttab_set_unmap_op(&unmap[i], vaddrs[i],
 				    GNTMAP_host_map, handles[i]);
 
-	if (HYPERVISOR_grant_table_op(GNTTABOP_unmap_grant_ref, unmap, i))
-		BUG();
+	BUG_ON(HYPERVISOR_grant_table_op(GNTTABOP_unmap_grant_ref, unmap, i));
 
 	err = GNTST_okay;
 	for (i = 0; i < nr_handles; i++) {
@@ -778,8 +776,7 @@ static int xenbus_unmap_ring_pv(struct xenbus_device *dev, void *vaddr)
 		unmap[i].handle = node->handles[i];
 	}
 
-	if (HYPERVISOR_grant_table_op(GNTTABOP_unmap_grant_ref, unmap, i))
-		BUG();
+	BUG_ON(HYPERVISOR_grant_table_op(GNTTABOP_unmap_grant_ref, unmap, i));
 
 	err = GNTST_okay;
 	leaked = false;