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_bl2_setup.c b/plat/socionext/uniphier/uniphier_bl2_setup.c
index daf0c45..e72b600 100644
--- a/plat/socionext/uniphier/uniphier_bl2_setup.c
+++ b/plat/socionext/uniphier/uniphier_bl2_setup.c
@@ -88,8 +88,12 @@
 		}
 	}
 
-	if (skip_scp)
-		uniphier_image_descs_fixup();
+	if (skip_scp) {
+		struct image_info *image_info;
+
+		image_info = uniphier_get_image_info(SCP_BL2_IMAGE_ID);
+		image_info->h.attr |= IMAGE_ATTRIB_SKIP_LOADING;
+	}
 }
 
 void bl2_platform_setup(void)