Revert "drm/amd/display: Restore 5s vbl offdelay for NV3x+ DGPUs"

Now that proper fixes have been found, let's revert this workaround.

This reverts commit a1fc7bf6677eb547167cb72b3bcafdc34b976692.

Tested-by: Mario Limonciello (AMD) <superm1@kernel.org>
Reviewed-by: Mario Limonciello (AMD) <superm1@kernel.org>
Signed-off-by: Leo Li <sunpeng.li@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit f64a9be5653689ff43e148cd8a6483077488c8e5)
Cc: stable@vger.kernel.org # 8382cd234981: drm/amd/display: consolidate DCN vblank/flip handling onto vupdate_no_lock
Cc: stable@vger.kernel.org # 48ab86360af1: drm/amd/display: check GRPH_FLIP status before sending event
Cc: stable@vger.kernel.org