image: Use gd->ram_base/_size in env_get_bootm_size()

Use only gd->ram_base/_size in env_get_bootm_size() instead of bi_dram[]
in some cases and bi_memstart in others.

Signed-off-by: Stefan Roese <sr@denx.de>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/common/image.c b/common/image.c
index 2ed46f7..6f68b13 100644
--- a/common/image.c
+++ b/common/image.c
@@ -685,13 +685,8 @@
 		return tmp;
 	}
 
-#if defined(CONFIG_ARM) || defined(CONFIG_MICROBLAZE)
-	start = gd->bd->bi_dram[0].start;
-	size = gd->bd->bi_dram[0].size;
-#else
-	start = gd->bd->bi_memstart;
-	size = gd->bd->bi_memsize;
-#endif
+	start = gd->ram_base;
+	size = gd->ram_size;
 
 	s = env_get("bootm_low");
 	if (s)