lock_all_ctx in setplane_internal may return -EINTR, and
__setplane_internal could return -EDEADLK. Making more
special cases for fb would make the code even harder to
read, so the easiest solution is not taking over the fb
refcount, and making callers responsible for dropping
the ref.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=102707
Fixes: 13736ba3 ("drm/legacy: Convert setplane ioctl locking to interruptible.")
Testcase: kms_atomic_interruptible
Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171220093545.613-2-maarten.lankhorst@linux.intel.comReviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>