drm/msm/dpu: Remove set but not used variables 'cmd_enc', 'priv'

Fixes gcc '-Wunused-but-set-variable' warning:

drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys_cmd.c: In function dpu_encoder_phys_cmd_ctl_start_irq:
drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys_cmd.c:136:31: warning: variable cmd_enc set but not used [-Wunused-but-set-variable]
drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys_cmd.c: In function dpu_encoder_phys_cmd_irq_control:
drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys_cmd.c:328:31: warning: variable cmd_enc set but not used [-Wunused-but-set-variable]
drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys_cmd.c: In function dpu_encoder_phys_cmd_tearcheck_config:
drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys_cmd.c:367:26: warning: variable priv set but not used [-Wunused-but-set-variable]
drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys_cmd.c: In function dpu_encoder_phys_cmd_wait_for_tx_complete:
drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys_cmd.c:662:31: warning: variable cmd_enc set but not used [-Wunused-but-set-variable]

They are not used since commit 25fdd593 ("drm/msm:
Add SDM845 DPU support")

Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: zhengbin <zhengbin13@huawei.com>
Signed-off-by: Rob Clark <robdclark@chromium.org>