gralloc: Use only metadata for color space

Currently both handle metadata and handle flags are used to indicate
the color space. This change deprecates support for flags.

Also gralloc doesn't set a color space based on use case anymore,
since front-end requirements keep changing. The default is set to 601
and the onus of correctly specifying the color space now rests on
clients.

CRs-fixed: 919117

Change-Id: I4988830e22804517b393c60dbe641d3bd1d790ec
diff --git a/libgralloc/gralloc_priv.h b/libgralloc/gralloc_priv.h
index 1370eac..38a6235 100644
--- a/libgralloc/gralloc_priv.h
+++ b/libgralloc/gralloc_priv.h
@@ -193,9 +193,9 @@
             PRIV_FLAGS_CAMERA_READ        = 0x00040000,
             PRIV_FLAGS_HW_COMPOSER        = 0x00080000,
             PRIV_FLAGS_HW_TEXTURE         = 0x00100000,
-            PRIV_FLAGS_ITU_R_601          = 0x00200000,
-            PRIV_FLAGS_ITU_R_601_FR       = 0x00400000,
-            PRIV_FLAGS_ITU_R_709          = 0x00800000,
+            PRIV_FLAGS_ITU_R_601          = 0x00200000, //Unused from display
+            PRIV_FLAGS_ITU_R_601_FR       = 0x00400000, //Unused from display
+            PRIV_FLAGS_ITU_R_709          = 0x00800000, //Unused from display
             PRIV_FLAGS_SECURE_DISPLAY     = 0x01000000,
             // Buffer is rendered in Tile Format
             PRIV_FLAGS_TILE_RENDERED      = 0x02000000,