Mark keymint as unfrozen to manage keystore2's imports

We are now checking the imports of frozen versions of interfaces and
need mark keystore2 as `frozen: false` so the aidl_interfaces that
import it will import the latest unfrozen version.

Test: hal_implementation_test
Bug: 257338648
Change-Id: Ibcb151abd2fc13e3f7dfbcf515d0f62839d1caf9
diff --git a/security/keymint/aidl/Android.bp b/security/keymint/aidl/Android.bp
index 6efff2f..5a76a21 100644
--- a/security/keymint/aidl/Android.bp
+++ b/security/keymint/aidl/Android.bp
@@ -17,6 +17,7 @@
         "android.hardware.security.secureclock-V1",
     ],
     stability: "vintf",
+    frozen: false,
     backend: {
         java: {
             platform_apis: true,