arm64: defconfig: Enable DRM_SUN8I_MIXER

Allwinner Display Engine 2.0 Mixer is need for ARM64
Allwinner SoC's, build it as module.
Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>
Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>

arch/arm64/configs/defconfig

@@ -450,6 +450,7 @@ CONFIG_DRM_EXYNOS_HDMI=y
 CONFIG_DRM_EXYNOS_MIC=y
 CONFIG_DRM_ROCKCHIP=m
 CONFIG_DRM_SUN4I=m
+CONFIG_DRM_SUN8I_MIXER=m
 CONFIG_ROCKCHIP_ANALOGIX_DP=y
 CONFIG_ROCKCHIP_CDN_DP=y
 CONFIG_ROCKCHIP_DW_HDMI=y