drm: Check locking in drm_for_each_fb
drm: Check locking in drm_for_each_fb

Ever since framebuffers are reference counted we have a special lock
for the global fb list. Make sure users of that list do hold that
lock when using the new iterators.

Reviewed-by: Maarten Lankhorst <743c2818a341d71b99ed2b566f9f80c2fc288f93@linux.intel.com>
Signed-off-by: Daniel Vetter <c1b6782c4af8f0673da8923a0702a1832e5940f4@intel.com>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs