gralloc: Add RGBA_5551 and RGBA_4444 formats

Define RGBA_5551 and RGBA_4444 which are OEM specific formats in
gralloc_priv.h

Change-Id: I6cdb723ea7e0783e7f58dbe1b45152dc427994c9
diff --git a/libgralloc/gralloc_priv.h b/libgralloc/gralloc_priv.h
index e8b3dfb..b60eaff 100755
--- a/libgralloc/gralloc_priv.h
+++ b/libgralloc/gralloc_priv.h
@@ -95,6 +95,8 @@
 
 /* OEM specific HAL formats */
 
+#define HAL_PIXEL_FORMAT_RGBA_5551               6
+#define HAL_PIXEL_FORMAT_RGBA_4444               7
 #define HAL_PIXEL_FORMAT_NV12_ENCODEABLE         0x102
 #define HAL_PIXEL_FORMAT_YCbCr_420_SP_VENUS      0x7FA30C04
 #define HAL_PIXEL_FORMAT_YCbCr_420_SP_TILED      0x7FA30C03