Fix bpp mismatch

Bug: 26980851

GL_RGBA16F was being incorrectly calculated
as 4 bpp instead of 16 in Texture's objectSize(),
leading to a mismatch in cache size tracking
in GradientCache

Change-Id: I533c52fcdf9910d7a7d14bbd80965b8cbef8e147
diff --git a/libs/hwui/Texture.cpp b/libs/hwui/Texture.cpp
index c09b6dd..49a103c 100644
--- a/libs/hwui/Texture.cpp
+++ b/libs/hwui/Texture.cpp
@@ -33,8 +33,11 @@
     case GL_RGB:
         return 3;
     case GL_RGBA:
-    default:
         return 4;
+    case GL_RGBA16F:
+        return 16;
+    default:
+        LOG_ALWAYS_FATAL("UNKNOWN FORMAT %d", glFormat);
     }
 }