Again this is neatly protected by the dev->master_mutex now. There is
a driver callback both for set and drop, but it's only used by vmwgfx.
And vmwgfx has it's own solid locking for shared resources (besides
dev->master_mutex), hence is all safe. Let's drop another place where
the drm legacy bkl is used.

Cc: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Emil Velikov <emil.l.velikov@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1466148814-8194-6-git-send-email-daniel.vetter@ffwll.ch