drm/msm/dpu: Fix smatch warnings about variable dereferenced before check

drm/msm/dpu: Fix smatch warnings about variable dereferenced before check

Fix below smatch warnings:
drivers/gpu/drm/msm/disp/dpu1/dpu_hw_sspp_v13.c:161 dpu_hw_sspp_setup_pe_config_v13()
warn: variable dereferenced before check 'ctx' (see line 159)

Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Dan Carpenter <error27@gmail.com>
Closes: https://lore.kernel.org/r/202601252214.oEaY3UZM-lkp@intel.com/
Signed-off-by: sunliming <sunliming@kylinos.cn>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
Patchwork: https://patchwork.freedesktop.org/patch/701853/
Link: https://lore.kernel.org/r/20260130053615.24886-1-sunliming@linux.dev
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>