Fix Sonata's memory layout.

Sonata starts the revokable memory range (the range that the shadow
memory covers) 0x80 bytes before the start of code memory, but the board
description file did not mention this.

sdk/boards/sonata.json

diff --git a/sdk/boards/sonata.json b/sdk/boards/sonata.json
index a79244d..1458f56 100644
--- a/sdk/boards/sonata.json
+++ b/sdk/boards/sonata.json
@@ -28,6 +28,7 @@
     "heap": {
         "end": 0x00140000
     },
+    "revokable_memory_start": 0x00100000,
     "interrupts": [
         {
             "name": "UartRxWatermark",