drm/msm/dpu: remove unused local variable 'cmd_enc'

drm/msm/dpu: remove unused local variable 'cmd_enc'

Fixes the following W=1 kernel build warning:

drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys_cmd.c: In function ‘dpu_encoder_phys_cmd_wait_for_commit_done’:
drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys_cmd.c:688:31: warning: variable ‘cmd_enc’ set but not used [-Wunused-but-set-variable]

Fixes: fe286893ed34 ("drm/msm/dpu: Remove unused call in wait_for_commit_done")
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
Link: https://lore.kernel.org/r/20210407083334.2762-1-thunder.leizhen@huawei.com
Reviewed-by: Abhinav Kumar <abhinavk@codeaurora.org>
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Signed-off-by: Rob Clark <robdclark@chromium.org>