Shrink partition table for EVT

- EVTs can come with 8GB eMMCs. u-boot seems to read these as ~7.3GiB,
so set the disk size small enough to fit, or it'll be rejected at flash
time.

Change-Id: If2ab2323a3f495880fba0a7dd1ef2ce2547dcffb
diff --git a/partition-table.json b/partition-table.json
index 9040ebc..a39a449 100644
--- a/partition-table.json
+++ b/partition-table.json
@@ -1,6 +1,6 @@
 {
   "settings": {
-    "disk_size": "12 GiB",
+    "disk_size": "7 GiB",
     "disk_alignment": "8 MiB",
     "disk_guid": "85b83f23-51c4-4403-8bac-906ff5800f4e"
   },
@@ -28,4 +28,4 @@
       "position": 3
     }
   ]
-}
\ No newline at end of file
+}