drm: Clear state->acquire_ctx before leaving drm_atomic_helper_commit_duplicated_state()

drm: Clear state->acquire_ctx before leaving drm_atomic_helper_commit_duplicated_state()

BugLink: https://bugs.launchpad.net/bugs/1837664
[ Upstream commit aa394b0dd68cb00c483e151dcd84713d4d517ed1 ]

drm_atomic_helper_commit_duplicated_state() sets state->acquire_ctx to
the context given in the argument and leaves it in state after it
quits. The lifetime of state and context are not guaranteed to be the
same, so we shouldn't leave that pointer hanging around. This patch
resets the context to NULL to avoid any oopses.

Changes in v2:
- Added to the set

Suggested-by: Daniel Vetter <daniel@ffwll.ch>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Sean Paul <seanpaul@chromium.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20181129150423.239081-1-sean@poorly.run
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>