gralloc: Use only 'data' member in GraphicsMetadata

- In gralloc3, first member 'size' in GraphicsMetadata struct was
  never unused in call to GetGraphicsMetadata. Get() call always
  returned 'data' member in GraphicsMetadata structure.

- Gralloc4 implementation introduced new encode/decode functions for
  GraphicsMetadata which are simultaneously used during set/get
  calls to encode/decode  metadata for caller and during storing/
  retrieving it from Metadata_t struct. Get() call returned
  GraphicsMetadata struct pointing to its first member 'size'
  instead of second member 'data'.

- Implement function to encode/decode GraphicsMetadataRaw to translate
  the metadata before calling mapper set/get.

- Update encodeGraphicsMetadata/decodeGraphicsMetadata functions to
  store/retrieve only 'data' member in GraphicsMetadata structure.

CRs-fixed: 2682060
Change-Id: I60c3dd2029ba21aa481dad35f9b4738b2d78957a
diff --git a/gralloc/QtiGrallocMetadata.h b/gralloc/QtiGrallocMetadata.h
index 00b0503..b8e779b 100644
--- a/gralloc/QtiGrallocMetadata.h
+++ b/gralloc/QtiGrallocMetadata.h
@@ -64,9 +64,10 @@
 
 // GRAPHICS_METADATA
 #define GRAPHICS_METADATA_SIZE 4096
+#define GRAPHICS_METADATA_SIZE_IN_BYTES (GRAPHICS_METADATA_SIZE * sizeof(uint32_t))
 typedef struct GraphicsMetadata {
-  uint32_t size;
-  uint32_t data[GRAPHICS_METADATA_SIZE];
+  uint32_t size;  //unused in Gralloc4, in Gralloc3 it was never returned on Get()
+  uint32_t data[GRAPHICS_METADATA_SIZE]; //Clients must set only raw data with Gralloc4
 } GraphicsMetadata;
 
 // UBWC_CR_STATS_INFO