yocto-bsp: filter out 'layer' from arch list

The yocto-layer tool added a new directory alongside the actual
architectures and 'common', which is already screened out as not an
actual architecture when displaying the architecures.

The same needs to be done for 'layer' which isn't actually an
architecuture and likewise needs to be screened out.

Fixes [YOCTO #4735].

(From meta-yocto master rev: 7459485bf75855a40d124915d38284f737a25cc4)

(From meta-yocto rev: 0af5b4550cdb836c68bb5b22fccb8d460fb7d515)

Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
Signed-off-by: Saul Wold <sgw@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

scripts/lib/bsp/engine.py

@@ -1674,7 +1674,7 @@ def yocto_bsp_list(args, scripts_path, properties_file):
         arch_path = bsp_path + '/substrate/target/arch'
         print "Architectures available:"
         for arch in os.listdir(arch_path):
-            if arch == "common":
+            if arch == "common" or arch == "layer":
                 continue
             print "    %s" % arch
         return True