libeffects: Add host support for preprocessing module

- Removed __unused that is not supported by host toolchain

Bug: 182485928
Test: AudioPreProcessingTest on host

Change-Id: I5b87ab71a7c785e5dc610770ddfe141864874c2b
diff --git a/media/libeffects/preprocessing/tests/Android.bp b/media/libeffects/preprocessing/tests/Android.bp
index 8848e79..806bc2b 100644
--- a/media/libeffects/preprocessing/tests/Android.bp
+++ b/media/libeffects/preprocessing/tests/Android.bp
@@ -13,6 +13,8 @@
 cc_test {
     name: "AudioPreProcessingTest",
     vendor: true,
+    host_supported: true,
+    gtest: false,
     srcs: ["PreProcessingTest.cpp"],
     shared_libs: [
         "libaudioutils",
@@ -27,7 +29,6 @@
         "libaudioeffects",
         "libhardware_headers",
     ],
-    gtest: false,
 }
 
 cc_test {