Add SOONG_NAMESPACES for mediaDrm plugin

* Without this CL, the following gs-common ag/29381547 will hit a
  duplicated name issue.

Bug: 364190751
Bug: 229298787
Bug: 366426322
Flag: EXEMPT castauth enabled
Test: ab/P80927970
Change-Id: I6bf2fe4ce933f70179cb83fa597caaf98806ffdc

cast_auth/mediadrm/Android.bp

@@ -1,7 +1,11 @@
-
 // ----------------------------------------------------------------------------
 // Builds android.hardware.drm-service.castkey
 //
+// TODO(b/366426322): Merge these targets into `device/google/gs-common`.
+
+soong_namespace {
+}
+
 package {
     // See: http://go/android-license-faq
     // A large-scale-change added 'default_applicable_licenses' to import
@@ -32,7 +36,10 @@ cc_defaults {
 
     relative_install_path: "hw",
 
-    cflags: ["-Wall", "-Werror"],
+    cflags: [
+        "-Wall",
+        "-Werror",
+    ],
 
     include_dirs: [
         "device/google/tangorpro/cast_auth/mediadrm/include",

device-tangorpro.mk

@@ -258,7 +258,10 @@ PRODUCT_VENDOR_PROPERTIES += \
 PRODUCT_SOONG_NAMESPACES += \
 	vendor/lib64
 
+# TODO(b/366426322): Merge CastKey Drm plugin into `device/google/gs-common`.
 # CastKey Drm plugin modules
+PRODUCT_SOONG_NAMESPACES += \
+	device/google/tangorpro/cast_auth/mediadrm
 PRODUCT_PACKAGES += \
 	android.hardware.drm-service.castkey