This reverts commit 869184a6.

This is required for the Sony Vaio Jesse was working on at the time, but
breaks most other eDP machines - machines that were working in earlier
kernels.
Reported-and-tested-by: NDave Airlie <airlied@redhat.com>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=31188Tested-by: NZhao Jian <jian.j.zhao@intel.com>
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>