treewide: fix GPLv2+ obsolete-license warnings

The LICENSE string 'GPLv2+' is considered obsolete by Yocto and raises a
warning.  Switch them too the accepted tag 'GPL-2.0-or-later'.

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: I88c639dbb45762e2e019a3503f1f1930b65c09d6
diff --git a/meta-hpe/meta-gxp/recipes-bsp/u-boot/u-boot-common-gxp_2020.10.inc b/meta-hpe/meta-gxp/recipes-bsp/u-boot/u-boot-common-gxp_2020.10.inc
index c8231c0..8b7b218 100644
--- a/meta-hpe/meta-gxp/recipes-bsp/u-boot/u-boot-common-gxp_2020.10.inc
+++ b/meta-hpe/meta-gxp/recipes-bsp/u-boot/u-boot-common-gxp_2020.10.inc
@@ -1,7 +1,7 @@
 HOMEPAGE = "https://github.com/HewlettPackard/gxp-uboot"
 DEPENDS += "flex-native bison-native bc-native"
 
-LICENSE = "GPLv2+"
+LICENSE = "GPL-2.0-or-later"
 LIC_FILES_CHKSUM = "file://Licenses/gpl-2.0.txt;md5=b234ee4d69f5fce4486a80fdaf4a4263"
 PE = "1"