Remove llndk_headers

Replace llndk_headers with cc_library_headers with
llndk.llndk_headers: true.

Bug: 170784825
Test: m checkbuild
Test: compare out/soong/build.ninja
Test: TestLlndkHeaders
Change-Id: I33b411cd4d474318796c2073375176b82dd8c216
diff --git a/cc/image.go b/cc/image.go
index 6265b13..66b02d9 100644
--- a/cc/image.go
+++ b/cc/image.go
@@ -437,7 +437,7 @@
 		productVndkVersion = platformVndkVersion
 	}
 
-	if m.IsLlndkLibrary() || m.IsLlndkHeaders() || m.NeedsLlndkVariants() {
+	if m.IsLlndkLibrary() || m.NeedsLlndkVariants() {
 		// This is an LLNDK library.  The implementation of the library will be on /system,
 		// and vendor and product variants will be created with LLNDK stubs.
 		// The LLNDK libraries need vendor variants even if there is no VNDK.