[keystore2] Fix binder import path

Import from the binder crate root instead of binder::public_api for
compatibility with the new crate structure.

Test: m
Bug: 196056781
Change-Id: Ia9695e5493bda965ca9a42989ec5a284407595ce
diff --git a/keystore2/src/maintenance.rs b/keystore2/src/maintenance.rs
index 57abc26..ca73820 100644
--- a/keystore2/src/maintenance.rs
+++ b/keystore2/src/maintenance.rs
@@ -155,7 +155,7 @@
 
     fn call_with_watchdog<F>(sec_level: SecurityLevel, name: &'static str, op: &F) -> Result<()>
     where
-        F: Fn(Strong<dyn IKeyMintDevice>) -> binder::public_api::Result<()>,
+        F: Fn(Strong<dyn IKeyMintDevice>) -> binder::Result<()>,
     {
         let (km_dev, _, _) = get_keymint_device(&sec_level)
             .context("In call_with_watchdog: getting keymint device")?;
@@ -169,7 +169,7 @@
 
     fn call_on_all_security_levels<F>(name: &'static str, op: F) -> Result<()>
     where
-        F: Fn(Strong<dyn IKeyMintDevice>) -> binder::public_api::Result<()>,
+        F: Fn(Strong<dyn IKeyMintDevice>) -> binder::Result<()>,
     {
         let sec_levels = [
             (SecurityLevel::TRUSTED_ENVIRONMENT, "TRUSTED_ENVIRONMENT"),