drm/hdlcd|mali: Drop drm_vblank_cleanup

IRQs are properly shut down, so it almost works as race-free shutdown.
Except the irq is stopped after the vblank stuff, so boom anyway.
Proper way would be to call drm_atomic_helper_shutdown before any of
the kms things gets stopped. So no harm in removing the
drm_vblank_cleanup here really.

Same story for both hdlcd and mali.

v2: Move misplaced malidp hunk to this patch (Liviu).

Cc: Liviu Dudau <liviu.dudau@arm.com>
Cc: Brian Starkey <brian.starkey@arm.com>
Acked-by: Liviu Dudau <liviu.dudau@arm.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170524145212.27837-17-daniel.vetter@ffwll.ch