Revert "drm/i915/dp: use VBT provided eDP params if available"

This reverts commit 869184a675662bddcdf76c5b95665272facff2b8.

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: Dave Airlie <airlied@redhat.com>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=31188
Tested-by: Zhao Jian <jian.j.zhao@intel.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>