uniphier: add a helper to get image_info

In the next commit, I will have more usecases to get struct image_info
from image ID.  It is better to make a helper function at a different
layer.  I do not need the current uniphier_image_descs_fixup() since
the code is small enough to be squashed into the caller side.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
diff --git a/plat/socionext/uniphier/uniphier.h b/plat/socionext/uniphier/uniphier.h
index 2af30df..b1a0572 100644
--- a/plat/socionext/uniphier/uniphier.h
+++ b/plat/socionext/uniphier/uniphier.h
@@ -42,7 +42,9 @@
 
 int uniphier_io_setup(unsigned int soc);
 int uniphier_check_image(unsigned int image_id);
-void uniphier_image_descs_fixup(void);
+
+struct image_info;
+struct image_info *uniphier_get_image_info(unsigned int image_id);
 
 int uniphier_scp_is_running(void);
 void uniphier_scp_start(void);