CHERRY-PICK: Move some field to optional for storage probing

BUG=none
TEST=manually test

Change-Id: I0bf2c4e8834eb3f68ad6b9dfc8137ca332336755
Original: Change-Id: I4cd4319369aa86e7dfbe6a7ddcf8d9376eb91661
Original: Reviewed-on: https://gerrit.chromium.org/gerrit/64191
Original: Reviewed-by: Katie Roberts-Hoffman <katierh@chromium.org>
Original: Commit-Queue: Katie Roberts-Hoffman <katierh@chromium.org>
Original: Tested-by: Katie Roberts-Hoffman <katierh@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/64737
Reviewed-by: Heng-ruey Hsu <henryhsu@chromium.org>
Tested-by: Heng-ruey Hsu <henryhsu@chromium.org>
Commit-Queue: Heng-ruey Hsu <henryhsu@chromium.org>
diff --git a/py/gooftool/probe.py b/py/gooftool/probe.py
index e19f6c9..e708ea8 100644
--- a/py/gooftool/probe.py
+++ b/py/gooftool/probe.py
@@ -727,9 +727,10 @@
     sectors = (open(size_path).read().strip()
                if os.path.exists(size_path) else '')
     ata_fields = ['vendor', 'model']
-    emmc_fields = ['type', 'name', 'hwrev', 'oemid', 'cid', 'manfid', 'prv']
+    emmc_fields = ['type', 'name', 'hwrev', 'oemid', 'manfid']
+    optional_fields = ['cid', 'prv']
     data = (_ReadSysfsFields(dev_path, ata_fields) or
-            _ReadSysfsFields(dev_path, emmc_fields) or
+            _ReadSysfsFields(dev_path, emmc_fields, optional_fields) or
             None)
     if not data:
       return None