bootstd: Add a separate log category for expo

This feature is different enough from bootstd that it probably deserves
its own log category. It cannot use a uclass since it is not a device.

Add a new category.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/boot/expo.c b/boot/expo.c
index e7c81a3..8b966b6 100644
--- a/boot/expo.c
+++ b/boot/expo.c
@@ -6,6 +6,8 @@
  * Written by Simon Glass <sjg@chromium.org>
  */
 
+#define LOG_CATEGORY	LOGC_EXPO
+
 #include <common.h>
 #include <dm.h>
 #include <expo.h>
diff --git a/boot/scene.c b/boot/scene.c
index 1383be2..43c978e 100644
--- a/boot/scene.c
+++ b/boot/scene.c
@@ -6,6 +6,8 @@
  * Written by Simon Glass <sjg@chromium.org>
  */
 
+#define LOG_CATEGORY	LOGC_EXPO
+
 #include <common.h>
 #include <dm.h>
 #include <expo.h>
diff --git a/boot/scene_menu.c b/boot/scene_menu.c
index 9ee911f..8b04d44 100644
--- a/boot/scene_menu.c
+++ b/boot/scene_menu.c
@@ -6,7 +6,7 @@
  * Written by Simon Glass <sjg@chromium.org>
  */
 
-#define LOG_CATEGORY	LOGC_BOOT
+#define LOG_CATEGORY	LOGC_EXPO
 
 #include <common.h>
 #include <dm.h>
diff --git a/common/log.c b/common/log.c
index 7cfc49b..6f02a25 100644
--- a/common/log.c
+++ b/common/log.c
@@ -31,6 +31,7 @@
 	"boot",
 	"event",
 	"fs",
+	"expo",
 };
 
 _Static_assert(ARRAY_SIZE(log_cat_name) == LOGC_COUNT - LOGC_NONE,
diff --git a/include/log.h b/include/log.h
index 3bab40b..6e84f080 100644
--- a/include/log.h
+++ b/include/log.h
@@ -102,6 +102,8 @@
 	LOGC_EVENT,
 	/** @LOGC_FS: Related to filesystems */
 	LOGC_FS,
+	/** @LOGC_EXPO: Related to expo handling */
+	LOGC_EXPO,
 	/** @LOGC_COUNT: Number of log categories */
 	LOGC_COUNT,
 	/** @LOGC_END: Sentinel value for lists of log categories */