recovery: Do not abort install on detecting older security patch level

 * This allows going back to stock ROM to progress

Change-Id: If8a3ab7347e51c90337c4044826226ea11d6a327
diff --git a/recovery.cpp b/recovery.cpp
index 6d20acd..eba367b 100644
--- a/recovery.cpp
+++ b/recovery.cpp
@@ -199,6 +199,15 @@
   }
 }
 
+bool ask_to_continue_spl_downgrade(Device* device) {
+  if (get_build_type() == "user") {
+    return false;
+  } else {
+    device->GetUI()->SetProgressType(RecoveryUI::EMPTY);
+    return yes_no(device, "This package will downgrade your SPL, which may cause data loss", "Install anyway?");
+  }
+}
+
 static bool ask_to_wipe_data(Device* device) {
   std::vector<std::string> headers{ "Format user data?", "This includes internal storage.", "THIS CANNOT BE UNDONE!" };
   std::vector<std::string> items{ " Cancel", " Format data" };