drm/msm/dsi: Add missing check for alloc_ordered_workqueue

Add check for the return value of alloc_ordered_workqueue as it may return
NULL pointer and cause NULL pointer dereference.

Signed-off-by: Jiasheng Jiang <jiasheng@iscas.ac.cn>
Reviewed-by: Abhinav Kumar <quic_abhinavk@quicinc.com>
Patchwork: https://patchwork.freedesktop.org/patch/517646/
Link: https://lore.kernel.org/r/20230110021651.12770-1-jiasheng@iscas.ac.cn


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