drm/i915/dp: Initialize eDP fixed mode in intel_dp_init

Since we do EDID caching in intel_dp_init, we can do the fixed mode
initialization there too. This should not change the functionality apart
from initializing fixed mode earlier. Particularly retain the behaviour of
only falling back to VBT if EDID is not available to not regress

commit 47f0eb22
Author: Keith Packard <keithp@keithp.com>
Date:   Mon Sep 19 14:33:26 2011 -0700

    drm/i915: Only use VBT panel mode on eDP if no EDID is found

Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>