rust: Use rust_ffi for Rust generated C libraries.

We no longer have the rust_library_shared and rust_library_static module
types. They've been renamed to rust_ffi_* instead. This brings
cargo2android.py up to date.

Bug: 175155132
Test: cargo2android's Android.bp for libquiche contains rust_ffi modules
Change-Id: I01bb8b4e56c41d36481ffd363f96aecb770d7cb8
diff --git a/scripts/cargo2android.py b/scripts/cargo2android.py
index fd4d736..cab2492 100755
--- a/scripts/cargo2android.py
+++ b/scripts/cargo2android.py
@@ -742,11 +742,11 @@
       self.stem = 'lib' + self.crate_name
       self.module_name = altered_name(self.stem) + '_dylib'
     elif crate_type == 'cdylib':  # rust_library[_host]_shared
-      self.module_type = 'rust_library' + host + '_shared'
+      self.module_type = 'rust_ffi' + host + '_shared'
       self.stem = 'lib' + self.crate_name
       self.module_name = altered_name(self.stem) + '_shared'
     elif crate_type == 'staticlib':  # rust_library[_host]_static
-      self.module_type = 'rust_library' + host + '_static'
+      self.module_type = 'rust_ffi' + host + '_static'
       self.stem = 'lib' + self.crate_name
       self.module_name = altered_name(self.stem) + '_static'
     elif crate_type == 'test':  # rust_test[_host]