[avb] Convert C enum to Rust enum in libavb_bindgen

C enums were converted to constants prior to this cl.

Bug: 237373557
Test: m pvmfw_img && atest libvbmeta_rust.test
Change-Id: I07137a1398741db91abff2cd3e65135d6203ddfb
diff --git a/libs/avb/Android.bp b/libs/avb/Android.bp
index a19a538..8bac942 100644
--- a/libs/avb/Android.bp
+++ b/libs/avb/Android.bp
@@ -12,6 +12,7 @@
     source_stem: "bindings",
     bindgen_flags: [
         "--size_t-is-usize",
+        "--default-enum-style rust",
         "--allowlist-function=.*",
         "--use-core",
         "--raw-line=#![no_std]",