Consistently use Bool instead of proptools.Bool

Use Bool instead of proptools.Bool and String instead of proptools.String.

Test: m checkbuild
Change-Id: I32d84add9f27128c7a65413e9612fd920613584f
diff --git a/cc/proto.go b/cc/proto.go
index 42bb536..22e50ab 100644
--- a/cc/proto.go
+++ b/cc/proto.go
@@ -19,7 +19,6 @@
 
 	"github.com/google/blueprint"
 	"github.com/google/blueprint/pathtools"
-	"github.com/google/blueprint/proptools"
 
 	"android/soong/android"
 )
@@ -114,7 +113,7 @@
 
 	flags.protoFlags = android.ProtoFlags(ctx, p)
 
-	if proptools.String(p.Proto.Type) == "lite" {
+	if String(p.Proto.Type) == "lite" {
 		flags.protoOutParams = append(flags.protoOutParams, "lite")
 	}