drm/exynos: Fix potential NULL pointer dereference in exynos_drm_encoder.c
drm/exynos: Fix potential NULL pointer dereference in exynos_drm_encoder.c

Check overlay_ops is not NULL as checked in the previous 'if' condition.
Fixes the following smatch error:
drivers/gpu/drm/exynos/exynos_drm_encoder.c:509 exynos_drm_encoder_plane_disable()
error: we previously assumed 'overlay_ops' could be null (see line 499)

Signed-off-by: Sachin Kamat <1c3b1584a6008857f36c03c58f657c0fc16fc09e@linaro.org>
Signed-off-by: Inki Dae <bae4a7a27bbc965064e97edd6e179ac4979db440@samsung.com>
Signed-off-by: Kyungmin Park <504c23c4986a3760712724894be3105092c27331@samsung.com>

KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs