drm/msm: fix workqueue leak on bind errors

In the Linux kernel, the following vulnerability has been resolved: drm/msm: fix workqueue leak on bind errors Make sure to destroy the workqueue also in case of early errors during bind (e.g. a subcomponent failing to bind). Since commit c3b790ea07a1 ("drm: Manage drm_mode_config_init with drmm_") the mode config will be freed when the drm device is released also when using the legacy interface, but add an explicit cleanup for consistency and to facilitate backporting. Patchwork: https://patchwork.freedesktop.org/patch/525093/