drm/msm/hdmi: Add missing check for alloc_ordered_workqueue

In the Linux kernel, the following vulnerability has been resolved:

drm/msm/hdmi: 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 in `hdmi_hdcp.c` and

`hdmi_hpd.c`.

Patchwork: https://patchwork.freedesktop.org/patch/517211/