drm/i915: remove now unnecessary delays in eDP panel power sequencing

Now that we're doing the right thing elsewhere, these are no longer
necessary.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=31114


Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>