drm/mediatek: Add vblank register/unregister callback functions

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: drm/mediatek: Add vblank register/unregister callback functions We encountered a kernel panic issue that callback data will be NULL when it's using in ovl irq handler. There is a timing issue between mtk_disp_ovl_irq_handler() and mtk_ovl_disable_vblank(). To resolve this issue, we use the flow to register/unregister vblank cb: - Register callback function and callback data when crtc creates. - Unregister callback function and callback data when crtc destroies. With this solution, we can assure callback data will not be NULL when vblank is disable.

References

• https://git.kernel.org/stable/c/8a2dbdeccef6de47565638abdf3c25f41cdffc37
• https://git.kernel.org/stable/c/8a265d9838bc3c63579002d55c2b2c655c4f8f26
• https://git.kernel.org/stable/c/3a4027b5971fe2a94e32754f007d9d3c12c68ad1
• https://git.kernel.org/stable/c/b74d921b900b6ce38c6247c0a1c86be9f3746493