swupdate_class: allow files with no fstype

Files in SWUPDATE_IMAGES with no fstype specified are currently skipped
when building the archive.  This changes the behaviour to include them
without appending an extension.

Together with the SWUPDATE_IMAGES_NOAPPEND_MACHINE flag this enables
inclusion of files from the deploy directory using the exact name in
SWUPDATE_IMAGES.

Signed-off-by: Mans Rullgard <mans@mansr.com>

classes/swupdate.bbclass

@@ -118,6 +118,9 @@ python do_swuimage () {
 
     for image in images:
         fstypes = (d.getVarFlag("SWUPDATE_IMAGES_FSTYPES", image, True) or "").split()
+        if not fstypes:
+            fstypes = [""]
+
         for fstype in fstypes:
 
             appendmachine = d.getVarFlag("SWUPDATE_IMAGES_NOAPPEND_MACHINE", image, True)