NAND boot: fix nand_load overlap issue

The code copy data from NAND flash block by block, so when
the data length isn't a whole-number multiple of the block
size, it will overlap the rest space.

Signed-off-by: Mingkai Hu <Mingkai.hu@freescale.com>
Signed-off-by: Scott Wood <scottwood@freescale.com>
diff --git a/nand_spl/nand_boot_fsl_elbc.c b/nand_spl/nand_boot_fsl_elbc.c
index 0d0c44e..7f14a6f 100644
--- a/nand_spl/nand_boot_fsl_elbc.c
+++ b/nand_spl/nand_boot_fsl_elbc.c
@@ -120,7 +120,7 @@
 
 			pos += page_size;
 			offs += page_size;
-		} while (offs & (block_size - 1));
+		} while ((offs & (block_size - 1)) && (pos < uboot_size));
 	}
 }