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

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

drivers/gpu/drm/msm/disp/dpu1/dpu_core_perf.c: In function dpu_core_perf_crtc_release_bw:
drivers/gpu/drm/msm/disp/dpu1/dpu_core_perf.c:248:25: warning: variable dpu_cstate set but not used [-Wunused-but-set-variable]
drivers/gpu/drm/msm/disp/dpu1/dpu_core_perf.c: In function dpu_core_perf_crtc_update:
drivers/gpu/drm/msm/disp/dpu1/dpu_core_perf.c:337:26: warning: variable priv 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>