Add LICENSE to uboot bitbake file

- yocto-2.3 enforces the rule to have LICENSE field set for
  all bitbake recipes.

Change-Id: I1cd1949099f765c0f10bc1bc637abc572eadd430
Signed-off-by: Saqib Khan <khansa@us.ibm.com>
diff --git a/common/recipes-bsp/u-boot/u-boot_2016.07.bb b/common/recipes-bsp/u-boot/u-boot_2016.07.bb
index 884758a..2800623 100644
--- a/common/recipes-bsp/u-boot/u-boot_2016.07.bb
+++ b/common/recipes-bsp/u-boot/u-boot_2016.07.bb
@@ -1,3 +1,4 @@
+LICENSE = "GPLv2+"
 require recipes-bsp/u-boot/u-boot.inc
 require u-boot.inc