gralloc: Change private usage flags from enums to defines

1. It helps in checking gralloc private usage flags at compile time.
2. Define GRALLOC_MODULE_PERFORM_GET_UBWC_FLAG to enable client to
   query the value of "PRIV_FLAGS_UBWC_ALIGNED" flag at run time.
3. Add ADRENO_PIXELFORMAT_NV12_EXT in defined Adreno Pixel formats
   to fix NV12_UBWC HAL pixel format conversion to Adreno format.

Change-Id: I78ccac98f1bd1bfbd2aa596ceb7a293f3d2e5f6e
diff --git a/libgralloc/adreno_utils.h b/libgralloc/adreno_utils.h
index 6cb7810..78f49da 100644
--- a/libgralloc/adreno_utils.h
+++ b/libgralloc/adreno_utils.h
@@ -36,6 +36,7 @@
     ADRENO_PIXELFORMAT_NV12          = 103,
     ADRENO_PIXELFORMAT_YUY2          = 107,
     ADRENO_PIXELFORMAT_B4G4R4A4      = 115,
+    ADRENO_PIXELFORMAT_NV12_EXT      = 506,  // NV12 with non-std alignment and offsets
     ADRENO_PIXELFORMAT_R8G8B8        = 508,  // GL_RGB8
     ADRENO_PIXELFORMAT_A1B5G5R5      = 519,  // GL_RGB5_A1
     ADRENO_PIXELFORMAT_R8G8B8X8_SRGB = 520,  // GL_SRGB8