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/vendor_snapshot.go b/cc/vendor_snapshot.go
index 2f68cca..c0082fb 100644
--- a/cc/vendor_snapshot.go
+++ b/cc/vendor_snapshot.go
@@ -180,16 +180,13 @@
 	if _, ok := m.linker.(*kernelHeadersDecorator); ok {
 		return false
 	}
-	// skip llndk_library and llndk_headers which are backward compatible
+	// skip LLNDK libraries which are backward compatible
 	if m.IsLlndk() {
 		return false
 	}
 	if _, ok := m.linker.(*llndkStubDecorator); ok {
 		return false
 	}
-	if _, ok := m.linker.(*llndkHeadersDecorator); ok {
-		return false
-	}
 
 	// Libraries
 	if l, ok := m.linker.(snapshotLibraryInterface); ok {