defconfig: display: enable mdp overlay0 writeback

This flag was removed by the automatic defconfig update during the
process of mainlining mdp driver patches that use this flag. Those
patches are merged, so re-enable it again.

Change-Id: I1dbe46962205fd027fdcfd353d1b7178cbe363cc
Signed-off-by: Huaibin Yang <huaibiny@codeaurora.org>
diff --git a/arch/arm/configs/msm8960_defconfig b/arch/arm/configs/msm8960_defconfig
index 9f3d72b..dc6ffc3 100644
--- a/arch/arm/configs/msm8960_defconfig
+++ b/arch/arm/configs/msm8960_defconfig
@@ -308,6 +308,7 @@
 CONFIG_FB_MSM_TRIPLE_BUFFER=y
 CONFIG_FB_MSM_MDP40=y
 CONFIG_FB_MSM_OVERLAY=y
+CONFIG_FB_MSM_OVERLAY0_WRITEBACK=y
 CONFIG_FB_MSM_MIPI_PANEL_DETECT=y
 CONFIG_FB_MSM_HDMI_MSM_PANEL=y
 CONFIG_BACKLIGHT_LCD_SUPPORT=y