ARM: multi_v7_defconfig: Enable Exynos DRM Mixer driver

Mixer driver is selected by CONFIG_DRM_EXYNOS_HDMI option. Since Exynos5433
HDMI does not require Mixer and there are separate options to select Mixer
and HDMI.
Signed-off-by: Andrzej Hajda <a.hajda@samsung.com>
Reviewed-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>

arch/arm/configs/multi_v7_defconfig

@@ -542,6 +542,7 @@ CONFIG_DRM_NOUVEAU=m
 CONFIG_DRM_EXYNOS=m
 CONFIG_DRM_EXYNOS_DSI=y
 CONFIG_DRM_EXYNOS_FIMD=y
+CONFIG_DRM_EXYNOS_MIXER=y
 CONFIG_DRM_EXYNOS_HDMI=y
 CONFIG_DRM_ROCKCHIP=m
 CONFIG_ROCKCHIP_ANALOGIX_DP=m