Remove module-level allows

Now that this codebase is more mature, remove allow directives so that
if we introduce issues, the compiler will tell us.

Bug: none
Test: compiles
Test: keystore2_test
Change-Id: If24b4ea40e0e2e1368e575e1e0bf6004bb318a42
diff --git a/keystore2/src/km_compat/lib.rs b/keystore2/src/km_compat/lib.rs
index 6e27b5c..5ece8a7 100644
--- a/keystore2/src/km_compat/lib.rs
+++ b/keystore2/src/km_compat/lib.rs
@@ -12,13 +12,14 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-// TODO: Once this is stable, remove this and document everything public.
-#![allow(missing_docs)]
+//! Export into Rust a function to create a KeyMintDevice and add it as a service.
 
+#[allow(missing_docs)] // TODO remove this
 extern "C" {
     fn addKeyMintDeviceService() -> i32;
 }
 
+#[allow(missing_docs)] // TODO remove this
 pub fn add_keymint_device_service() -> i32 {
     unsafe { addKeyMintDeviceService() }
 }