drm/msm/dpu: avoid unnecessary check in DPU reservations

Return immediately on failure, this will make dpu reservations
part look cleaner.

Signed-off-by: Kalyan Thota <quic_kalyant@quicinc.com>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Reviewed-by: Marijn Suijten <marijn.suijten@somainline.org>
Patchwork: https://patchwork.freedesktop.org/patch/522442/
Link: https://lore.kernel.org/r/1676286704-818-4-git-send-email-quic_kalyant@quicinc.com


[DB: fixed merge conflict with b6975693, retain those changes]
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>