dist, dev: fix etherswitch upgrade script

The aforementioned upgrader in [1] assumes every option in [system]
has a delimiting '.', and also seems to do its rewriting work a bit too
unconditionally.  Most checkpoints in the wild don't have this device,
in which case this script should be a safe no-op.

[1] 2aa4d7b  dist, dev: Fixed the packet ordering in etherswitch

Change-Id: Icfd0350985109df1628eb9ab864cda42c54060a8
Reviewed-by: Gabor Dozsa <gabor.dozsa@arm.com>

util/cpt_upgraders/etherswitch.py

@@ -4,6 +4,7 @@ def upgrader(cpt):
             options = cpt.items(sec)
             for it in options:
                 opt_split = it[0].split('.')
+                if len(opt_split) < 2: continue
                 new_sec_name = opt_split[1]
                 old_opt_name = opt_split[len(opt_split) - 1]
                 if "outputFifo" in new_sec_name: