meta/meta-selftest/meta-skeleton: Update LICENSE variable to use SPDX license identifiers

An automated conversion using scripts/contrib/convert-spdx-licenses.py to
convert to use the standard SPDX license identifiers. Two recipes in meta-selftest
were not converted as they're that way specifically for testing. A change in
linux-firmware was also skipped and may need a more manual tweak.

(From OE-Core rev: ceda3238cdbf1beb216ae9ddb242470d5dfc25e0)

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta-selftest/recipes-test/devtool/devtool-test-local_6.03.bb

@@ -1,4 +1,4 @@
-LICENSE = "GPLv2+"
+LICENSE = "GPL-2.0-or-later"
 LIC_FILES_CHKSUM = "file://COPYING;md5=0636e73ff0215e8d672dc4c32c317bb3"
 
 INHIBIT_DEFAULT_DEPS = "1"

meta-selftest/recipes-test/devtool/devtool-test-patch-gz.bb

@@ -1,4 +1,4 @@
-LICENSE = "GPLv2+"
+LICENSE = "GPL-2.0-or-later"
 LIC_FILES_CHKSUM = "file://COPYING;md5=94d55d512a9ba36caa9b7df079bae19f"
 
 DEPENDS = "libxres libxext virtual/libx11 ncurses"

meta-selftest/recipes-test/devtool/devtool-upgrade-test2_git.bb

@@ -1,7 +1,7 @@
 SUMMARY = "A simple tool to wait for a specific signal over DBus"
 HOMEPAGE = "http://git.yoctoproject.org/cgit/cgit.cgi/dbus-wait"
 SECTION = "base"
-LICENSE = "GPLv2"
+LICENSE = "GPL-2.0-only"
 LIC_FILES_CHKSUM = "file://COPYING;md5=b234ee4d69f5fce4486a80fdaf4a4263"
 
 DEPENDS = "dbus"

meta-selftest/recipes-test/devtool/devtool-upgrade-test2_git.bb.upgraded

@@ -1,7 +1,7 @@
 SUMMARY = "A simple tool to wait for a specific signal over DBus"
 HOMEPAGE = "http://git.yoctoproject.org/cgit/cgit.cgi/dbus-wait"
 SECTION = "base"
-LICENSE = "GPLv2"
+LICENSE = "GPL-2.0-only"
 LIC_FILES_CHKSUM = "file://COPYING;md5=b234ee4d69f5fce4486a80fdaf4a4263"
 
 DEPENDS = "dbus"