Gralloc: Update layer_count while calling size calculation APIs

Set correct layer_count value for BufferInfo object.

Change-Id: If720fe286d21b8398706ca71aa2eb1e5fae1b968
diff --git a/gralloc/gr_buf_mgr.cpp b/gralloc/gr_buf_mgr.cpp
index 5cf18aa..12fd13f 100644
--- a/gralloc/gr_buf_mgr.cpp
+++ b/gralloc/gr_buf_mgr.cpp
@@ -326,6 +326,7 @@
   int buffer_type = GetBufferType(format);
   BufferInfo info = GetBufferInfo(descriptor);
   info.format = format;
+  info.layer_count = layer_count;
 
   bool use_adreno_for_size = false;
   GraphicsMetadata graphics_metadata = {};