[new uImage] Fix build issue on ARM

ARM platforms don't have a bd->bi_memsize so use bd->bi_dram[0].size instead.

Signed-off-by: Kumar Gala <galak@kernel.crashing.org>

common/image.c

@@ -463,8 +463,10 @@ ulong getenv_bootm_low(void)
 		return tmp;
 	}
 
-#ifdef CFG_SDRAM_BASE
+#if defined(CFG_SDRAM_BASE)
 	return CFG_SDRAM_BASE;
+#elif defined(CONFIG_ARM)
+	return gd->bd->bi_dram[0].start;
 #else
 	return 0;
 #endif
@@ -478,7 +480,11 @@ ulong getenv_bootm_size(void)
 		return tmp;
 	}
 
+#if defined(CONFIG_ARM)
+	return gd->bd->bi_dram[0].size;
+#else
 	return gd->bd->bi_memsize;
+#endif
 }
 
 void memmove_wd (void *to, void *from, size_t len, ulong chunksz)