dm: define LOG_CATEGORY for all uclass

Define LOG_CATEGORY for all uclass to allow filtering with
log command.

Signed-off-by: Patrick Delaunay <patrick.delaunay@foss.st.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/nvme/nvme-uclass.c b/drivers/nvme/nvme-uclass.c
index 610166d..239a92a 100644
--- a/drivers/nvme/nvme-uclass.c
+++ b/drivers/nvme/nvme-uclass.c
@@ -4,6 +4,8 @@
  * Copyright (C) 2017 Bin Meng <bmeng.cn@gmail.com>
  */
 
+#define LOG_CATEGORY UCLASS_NVME
+
 #include <common.h>
 #include <dm.h>