potter: update display flags

Change-Id: I039446b9cddf0d4e5c039e0b1414be8cd6eaec4e

BoardConfig.mk

@@ -99,7 +99,10 @@ BOARD_USES_ADRENO := true
 NUM_FRAMEBUFFER_SURFACE_BUFFERS := 3
 OVERRIDE_RS_DRIVER := libRSDriver_adreno.so
 TARGET_USES_C2D_COMPOSITION := true
+TARGET_USES_GRALLOC1 := true
 TARGET_USES_ION := true
+TARGET_USES_HWC2 := true
+TARGET_USES_OVERLAY := true
 TARGET_USES_NEW_ION_API := true
 USE_OPENGL_RENDERER := true
 MAX_EGL_CACHE_KEY_SIZE := 12*1024