drm/msm/dpu: replace IS_ERR_OR_NULL with IS_ERR during DSC init

Using IS_ERR_OR_NULL() together with PTR_ERR() is a typical mistake. If
the value is NULL, then the function will return 0 instead of a proper
return code. Moreover dpu_hw_dsc_init() can not return NULL.
Replace the IS_ERR_OR_NULL() call with IS_ERR().

This follows the commit 740828c7 ("drm/msm/dpu: fix error handling
in dpu_rm_init"), which removed IS_ERR_OR_NULL() from RM init code, but
then the commit f2803ee9 ("drm/msm/disp/dpu1: Add DSC support in
RM") added it for DSC init.

Suggested-by: Marijn Suijten <marijn.suijten@somainline.org>
Reviewed-by: Marijn Suijten <marijn.suijten@somainline.org>
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Patchwork: https://patchwork.freedesktop.org/patch/538203/
Link: https://lore.kernel.org/r/20230519234025.2864377-2-dmitry.baryshkov@linaro.org


Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>