drm: omapdrm: Add missing check for alloc_ordered_workqueue

drm: omapdrm: Add missing check for alloc_ordered_workqueue

commit e794b7b9b92977365c693760a259f8eef940c536 upstream.

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

Cc: stable@vger.kernel.org
Fixes: 2f95bc6d324a ("drm: omapdrm: Perform initialization/cleanup at probe/remove time")
Signed-off-by: Ma Ke <make24@iscas.ac.cn>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240808061336.2796729-1-make24@iscas.ac.cn
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>