BPF: rename bpf_defaults to bpf_cc_defaults

With the addition of defaults to the bpf soong module (see aosp/3249485
), the name `bpf_defaults` will be used to define defaults for bpf
program compilation. While there are separate soong namespaces for
module types and module names, rename the existing bpf_defaults
cc_defaults to bpf_cc_defaults for clarity.

While we're at it, add -Wextra, and cleanup unnecessary cflags in
clauses which use bpf_cc_defaults.

Test: TH
Change-Id: Ia6e69a7ae447490ddc7bc3e08f2d07753bae0eac
Signed-off-by: Neill Kapron <nkapron@google.com>
diff --git a/Android.bp b/Android.bp
index b8cd7b3..9a17183 100644
--- a/Android.bp
+++ b/Android.bp
@@ -16,10 +16,11 @@
 }
 
 cc_defaults {
-    name: "bpf_defaults",
+    name: "bpf_cc_defaults",
     cflags: [
         "-Wall",
         "-Werror",
+        "-Wextra",
         "-Wnullable-to-nonnull-conversion",
         "-Wthread-safety",
         "-Wunused-parameter",