api: export LCD device to external apps

This patch exports LCD info-query and bitmap-rendering functions to
external apps.

This patch is tested on a Seaboard.  Because the LCD driver is not yet
upstreamed, the test was done in a local downstream repo.

Signed-off-by: Che-Liang Chiou <clchiou@chromium.org>
diff --git a/api/api_private.h b/api/api_private.h
index 94a7fc5..988f702 100644
--- a/api/api_private.h
+++ b/api/api_private.h
@@ -45,4 +45,8 @@
 
 void dev_stor_init(void);
 
+int display_get_info(int type, struct display_info *di);
+int display_draw_bitmap(ulong bitmap, int x, int y);
+void display_clear(void);
+
 #endif /* _API_PRIVATE_H_ */