drm/exynos: select CEC_CORE if CEC_NOTIFIER

If the s5p-cec driver is a module and the drm exynos driver is built-in, then
the CEC core will be a module also, causing the CEC notifier to fail (will be
		compiled as empty functions).

To prevent this select CEC_CORE if CEC_NOTIFIER is set to ensure the CEC core
is also built into the kernel.
Signed-off-by: NHans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: NInki Dae <inki.dae@samsung.com>

drivers/gpu/drm/exynos/Kconfig

@@ -75,6 +75,7 @@ config DRM_EXYNOS_DP
 config DRM_EXYNOS_HDMI
 	bool "HDMI"
 	depends on DRM_EXYNOS_MIXER || DRM_EXYNOS5433_DECON
+	select CEC_CORE if CEC_NOTIFIER
 	help
 	  Choose this option if you want to use Exynos HDMI for DRM.