Use "gfxstream" namespace

Bug: b/271464937
Test: cd device/generic/goldfish-opengl/system && mma
Change-Id: I28efa08368b4798005dd954e0a4e856619250ab0
diff --git a/system/vulkan_enc_unit_tests/CommandBufferStagingStream_test.cpp b/system/vulkan_enc_unit_tests/CommandBufferStagingStream_test.cpp
index 375bc6e..dc18142 100644
--- a/system/vulkan_enc_unit_tests/CommandBufferStagingStream_test.cpp
+++ b/system/vulkan_enc_unit_tests/CommandBufferStagingStream_test.cpp
@@ -9,6 +9,9 @@
 #include <string_view>
 #include <thread>
 
+namespace gfxstream {
+namespace vk {
+
 using ::testing::A;
 using ::testing::ElementsAre;
 using ::testing::Eq;
@@ -721,4 +724,7 @@
 
     EXPECT_DEATH({ (void)stream.allocBuffer(kTestBufferSize); }, "")
         << "allocBuffer() should not be called while previous data is being flushed";
-}
\ No newline at end of file
+}
+
+}  // namespace vk
+}  // namespace gfxstream