drm/atomic-helper: remove backoff hack from disable/update_plane

We can now properly retry at the top level, yay!

v2: Also remove the temporary acquire_ctx hack again, no longer
needed!

Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170322215058.8671-6-daniel.vetter@ffwll.ch
2 files changed