drm/msm/dpu: Remove unneeded semicolon in dpu_encoder.c

Fixes coccicheck warning:

drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c:2260:3-4: Unneeded semicolon

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