drm/exynos: ipp: rename cmd_lock to lock

The ippdrv->cmd_list requires cmd_lock.
So renames cmd_lock to lock for context.

Signed-off-by: YoungJun Cho <yj44.cho@samsung.com>
Acked-by: Seong-Woo Kim <sw0312.kim@samsung.com>
Acked-by: Kyungmin Park <kyungmin.park@samsung.com>
Tested-by: Andrzej Hajda <a.hajda@samsung.com>
Signed-off-by: Inki Dae <inki.dae@samsung.com>

diff --cc drivers/gpu/drm/exynos/exynos_drm_ipp.c
Simple merge

diff --cc drivers/gpu/drm/exynos/exynos_drm_ipp.h
Simple merge