Rename control file.

The external updater only copies over files prefixed with
cargo2android to the new location, so the current version of the file
means the updater fails.

Test: Update the package.
Change-Id: Ifd5355cd7db91cf16459c071a06979d216ff4356
diff --git a/extra-module.bp b/cargo2android-extra-module.bp
similarity index 100%
rename from extra-module.bp
rename to cargo2android-extra-module.bp
diff --git a/cargo2android.json b/cargo2android.json
index 3668ba2..530205a 100644
--- a/cargo2android.json
+++ b/cargo2android.json
@@ -4,5 +4,5 @@
   "run": true,
   "tests": true,
   "copy-out": true,
-  "add-toplevel-block": "extra-module.bp"
+  "add-toplevel-block": "cargo2android-extra-module.bp"