create-spdx: handle CLOSED license

The special CLOSED license means that this is closed source code with
no other licensing assertions.  It's not a generic license in oe-core,
and not a SPDX license, so transform it to NONE explicitly.

(From OE-Core rev: b71bfba1b5076ad1b9a10c08ef0e3393ccbed92a)

Signed-off-by: Ross Burton <ross.burton@arm.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/classes/create-spdx.bbclass

@@ -105,6 +105,9 @@ def convert_license_to_spdx(lic, document, d, existing={}):
         if l == "|":
             return "OR"
 
+        if l == "CLOSED":
+            return "NONE"
+
         spdx_license = d.getVarFlag("SPDXLICENSEMAP", l) or l
         if spdx_license in license_data["licenses"]:
             return spdx_license