[PATCH v3] drm/exynos: fix display power call issue.

Changelog v3: make exynos_drm_display_power function use exynos_drm_best_encoder function instead of connector->encoder to get a valid encoder. connector->encoder could be NULL because with DRM_IOCTL_MODE_RMFB request, connector->encoder is NULL so fix this issue. Changelog v2: remove static prefi

[PATCH v3] drm/exynos: fix display power call issue.

Changelog v3: make exynos_drm_display_power function use exynos_drm_best_encoder function instead of connector->encoder to get a valid encoder. connector->encoder could be NULL because with DRM_IOCTL_MODE_RMFB request, connector->encoder is NULL so fix this issue. Changelog v2: remove static prefi