[new uImage] Provide ability to restrict region used for boot images

Allow the user to set 'bootm_low' and 'bootm_size' env vars as a way
to restrict what memory range is used for bootm.

Signed-off-by: Kumar Gala <galak@kernel.crashing.org>
Acked-by: Marian Balakowicz <m8@semihalf.com>
diff --git a/common/cmd_bootm.c b/common/cmd_bootm.c
index a32a5a2..8595ef6 100644
--- a/common/cmd_bootm.c
+++ b/common/cmd_bootm.c
@@ -124,6 +124,7 @@
 	ulong		os_data, os_len;
 	ulong		image_start, image_end;
 	ulong		load_start, load_end;
+	ulong		mem_start, mem_size;
 
 	struct lmb lmb;
 
@@ -134,11 +135,10 @@
 
 	lmb_init(&lmb);
 
-#ifdef CFG_SDRAM_BASE
-	lmb_add(&lmb, CFG_SDRAM_BASE, gd->bd->bi_memsize);
-#else
-	lmb_add(&lmb, 0, gd->bd->bi_memsize);
-#endif
+	mem_start = getenv_bootm_low();
+	mem_size = getenv_bootm_size();
+
+	lmb_add(&lmb, mem_start, mem_size);
 
 	board_lmb_reserve(&lmb);