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

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: 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>