Revert "GATT: Fix GATT error response for execute write"

This reverts commit b8a5b213a63def7c0a0d09d322603ae5a9abd435.

Reason for revert: This patch does not make Fluoride comply with BT Spec,
it just make a false assumption to pass a test case.

Change-Id: I023b7673c52522e7c1a318f5b9596ebb4fbc99ec
diff --git a/stack/gatt/gatt_sr.cc b/stack/gatt/gatt_sr.cc
index 35bd993..008702c 100644
--- a/stack/gatt/gatt_sr.cc
+++ b/stack/gatt/gatt_sr.cc
@@ -327,7 +327,7 @@
   } else /* nothing needs to be executed , send response now */
   {
     LOG(ERROR) << "gatt_process_exec_write_req: no prepare write pending";
-    gatt_send_error_rsp(tcb, GATT_INVALID_OFFSET, GATT_REQ_EXEC_WRITE, 0, false);
+    gatt_send_error_rsp(tcb, GATT_ERROR, GATT_REQ_EXEC_WRITE, 0, false);
   }
 }