Replace sRGB_888 with sRGB_X_8888

Bug: 10357459
Change-Id: I23a3eca77acd8b4b40b1a67e7c050a7245b1821a
diff --git a/include/system/graphics.h b/include/system/graphics.h
index 5d883be..154f9cb 100644
--- a/include/system/graphics.h
+++ b/include/system/graphics.h
@@ -75,7 +75,7 @@
      *
      */
     HAL_PIXEL_FORMAT_sRGB_A_8888        = 0xC,
-    HAL_PIXEL_FORMAT_sRGB_888           = 0xD,
+    HAL_PIXEL_FORMAT_sRGB_X_8888        = 0xD,
 
     /*
      * 0x100 - 0x1FF