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/usb/host/usb-uclass.c b/drivers/usb/host/usb-uclass.c
index e3b616c..fd39c33 100644
--- a/drivers/usb/host/usb-uclass.c
+++ b/drivers/usb/host/usb-uclass.c
@@ -6,6 +6,8 @@
  * usb_match_device() modified from Linux kernel v4.0.
  */
 
+#define LOG_CATEGORY UCLASS_USB
+
 #include <common.h>
 #include <dm.h>
 #include <errno.h>