drm_hwcomposer: Don't use Mapper@4 metadata API for legacy getters

As it turned out Mapper@4 metadata API calls are slow.
Allow using legacy getters again.

Closes: https://gitlab.freedesktop.org/drm-hwcomposer/drm-hwcomposer/-/issues/56

Signed-off-by: Roman Stratiienko <roman.o.stratiienko@globallogic.com>
diff --git a/bufferinfo/BufferInfoGetter.cpp b/bufferinfo/BufferInfoGetter.cpp
index 7f7f8ae..c284365 100644
--- a/bufferinfo/BufferInfoGetter.cpp
+++ b/bufferinfo/BufferInfoGetter.cpp
@@ -32,17 +32,17 @@
 
 BufferInfoGetter *BufferInfoGetter::GetInstance() {
   static std::unique_ptr<BufferInfoGetter> inst;
-  if (inst == nullptr) {
-#if PLATFORM_SDK_VERSION >= 30
+  if (!inst) {
+#if PLATFORM_SDK_VERSION >= 30 && defined(USE_IMAPPER4_METADATA_API)
     inst.reset(BufferInfoMapperMetadata::CreateInstance());
-    if (inst == nullptr) {
+    if (!inst) {
       ALOGW(
           "Generic buffer getter is not available. Falling back to legacy...");
-#endif
-      inst = LegacyBufferInfoGetter::CreateInstance();
-#if PLATFORM_SDK_VERSION >= 30
     }
 #endif
+    if (!inst) {
+      inst = LegacyBufferInfoGetter::CreateInstance();
+    }
   }
 
   return inst.get();